Gratuity Calculation

Dear Excel Experts,

Please help me in calculating the Gratuity as per the rules based on the Excel Sheet attached.

Rule: If service is less than 1 yr then no gratuity,
if service is more than 1 yr and less than 5 yrs then gratuity should be calculated on 21 days per year for 5 yrs on basic pay,
if gratuity is more than 5 yrs, then gratuity should be calculated on 21 days per year for 1st 5 Years and the remaining years on 30 days calculation basis on basic pay

Regards,
Fareed