Hi I need some help with this problem:

Harjap completed his program at Nova Scotia Community College in December. On June 30, he paid all the intereset that had accrued (at prime plus 2.5%) on his $5800 Canada Student Loan during the six month grace period. He selected the fixed rate options (prime plus 5%) and agreed to make end-of month payment of $95 beginning July 31. The prime rate was 8% at the beginining of the grace period and rose by 0.5% effective March 29. On August 13, the Prime rate rose another 0.5%. The revelent february had 28 days.

a) what amount of interest accrued during the grace period?

b)Calculate the total interested paid in the first threee regular payments and the balance owed after the third payment.

Formula: I=Pr1t1 + Pr2t2

I would really appreciate if you could help me out here.