Personnel Calculation Rule (PCR) for 24 to 27 days

Hi Experts,

I want to write a PCR for 24,25 and 26 days of a Calendar Month as per client requirement. Scenario is

If calendar days are 31 days then paid days must be 27.

If calendar days are 30 days then paid days must be 26.

For the month of February,

If calendar days are 29 days then paid days must be 25.

If calendar days are 28 days then paid days must be 24.

As there are 4 days off unpaid for every month.

Example:

Total Basic salary = 10000 for a month (If calendar days are 30 days then paid days must be 26)

one leave without pay 10000/26 = 384.62 per day

Salary payable for this month 25*384.62 = 9615.38

Please guide me to write this PCR.

Regards,

Atif