Help me to process Payroll

Hi experts!

Now, I'm working on payroll internationnal.

I want to build formula of payroll for employee

base pay = base salary grade * coefficient of pay.

example: base salary grade = 100

coefficient of pay = 2.

--> base pay = 2 * 100 = 200.

Gross income = base pay + bonus

If Employee vacaion without pay then Gross income = Base pay - number day that Employee vacation without pay * ( base pay / total day in month) + bonus.

Example: payroll of employ in January.

- Base pay = 200

- Number day that Employee vacation without pay = 2;

- Total day in month = 20

- Bonus = 50.

Gross income = 200 - 2 * ( 200 / 20 ) + 50 = 230.

Can you help me to process the problem, special to build Schema, rule and operation please?

Regrads, Huy