Hi Maggy,

Thank you for your comments!

In my opinion, you should derive the daily rate then multiply it by the number of days (or working days) of the pay period.

DailyRate = 7500 / OldWorkingDays_Feb1To15
BasicRate = DailyRate * NewWorkingDays_Feb1To10

Alternatively, you can use:
DailyRate = 7500 / DaysFor_Feb1To15
BasicRate = DailyRate * DaysFor_Feb1To10
Ex: (7,500/15)*10 -for Feb. 1-10, 2013 days computation

I think this may depend on company policies but pls. note that I'm not sure if the government has any regulations regarding computations of the basic rate.