i am working in one project related space booking.booked a space based on day/week/month with different price. i have created one class for calculate price either or like allow only hourly/day booking,some space avail for only day/month booking and some space allow for day/week and month and vice-versa.

public class PriceCalculation {     /// <summary>     /// Total Days     /// </summary>     public int TotalDays { get; }     /// <summary>     ///Open Days In One Week     /// </summary>     public int DaysInWeek { get; }     /// <summary>     /// Initializes a new instance of the PriceCalculation to the specified totalDays and daysInWeek     /// </summary>     /// <param name="totalDays">total number days</param>     /// <param name="daysInWeek">total open day in week</param>     public PriceCalculation(int totalDays,int daysInWeek)     {         TotalDays = totalDays;         DaysInWeek = daysInWeek;     }     public double CalculateDailyPrice(double pricePerDay)     {         return TotalDays * pricePerDay;     }     public double CalculateWeeklyPrice(int pricePerWeek)     {         var week = TotalDays / DaysInWeek;         return  week * pricePerWeek;     }     public double CalculateMonthlyPrice(int pricePerMonth)     {         var month = TotalDays / (DaysInWeek * 4);         return month * pricePerMonth;     }     public double CalculateDailyAndWeeklyPrice(double pricePerDay, int pricePerWeek)     {         var week = TotalDays / DaysInWeek;         var extraDays = TotalDays % DaysInWeek;         var week = TotalDays / DaysInWeek;         var extraDays = TotalDays % DaysInWeek;         return ((week * pricePerWeek) + (extraDays * pricePerDay));     }     public double CalculateDailyAndMonthlyPrice(double pricePerDay, int pricePerMonth)     {         var month = TotalDays / (DaysInWeek * 4);         var extradays = TotalDays - ((DaysInWeek * 4) * month);         var totalPrice = month * pricePerMonth;         return totalPrice + (extradays * pricePerDay);     }     public double CalculateWeeklyAndMonthlyPrice(int pricePerWeek, int pricePerMonth)     {         var month = TotalDays / (DaysInWeek * 4);         var extradays = TotalDays - ((DaysInWeek * 4) * month);         var totalPrice = month * pricePerMonth;         var week = extradays / DaysInWeek;         return totalPrice + (week * pricePerWeek);     }     public double CalculatePrice(double pricePerDay,int pricePerWeek, int pricePerMonth)     {          double totalPrice = 0;         if (TotalDays >= (DaysInWeek * 4))         {             var month = TotalDays / (DaysInWeek * 4);             totalPrice = month * pricePerMonth;             var extradays = TotalDays - ((DaysInWeek * 4) * month);             if (extradays >= DaysInWeek)             {                 var week = extradays / DaysInWeek;                 extradays = extradays % DaysInWeek;                 totalPrice = totalPrice + (week * pricePerWeek) + (extradays * pricePerDay);             }             else             {                 totalPrice = totalPrice + (extradays * pricePerDay);             }         }         else if (TotalDays >= DaysInWeek)         {                 var week = TotalDays / DaysInWeek;                 var extraDays = TotalDays % DaysInWeek;                 totalPrice = (week * pricePerWeek) + (extraDays * pricePerDay);           }         else         {             totalPrice = (TotalDays * pricePerDay);         }         return totalPrice;     } } 

now if space only available for Day/Week booking then

 PriceCalculation calculation = new PriceCalculation(8, 7); 

for this situation i have called method for day/week calculation

totalPrice = calculation.CalculateDailyAndWeeklyPrice(88,165);//consider as 1 week and 1 day calculate. 

this code working fine. now my question is in my code required changes for calculation based on

booking 7-26 days would be charged ($ 165 + (total days-7)*(week rate/7))1.5%

like above. now how to design my class for this pricecalculation and it not affect in future changes. please take look at into above code.