Meredith deposits 12 into an account at the end of each day

Meredith deposits $12 into an account at the end of each day in 1989 and 1990 and $15 at the end of each day in 1991. The account earns 9% per year compounded annually in 1989 and 1990 and 12% per year compounded semiannually in 1991. Find the amount in Meredith’s account on December 31, 1991

Solution

for the 1st 2 years interest is calculated annually.

so, deposit for 1st year = 365*12 and adding interest = 365*12*1.09 = 4774.2..
deposit after 2nd year = 4774.2 + ( 365*12) = 9154.2 and adding interest = 9978.078..

Now, interest is calcualte twice for the last year.
for at 1st half of the year , total deposit = 9978.078 + ( 15*181) =12693.078..and after adding interest = 14216.24736..
and amount on the last day of the year = ( 14216.24736 + (184*15) ) * 1.12 = 19013.39704...