The Smith family has a circular garden with a diameter of 22 feet. They cover the garden with mulch. The cost of the mulch is $1.25 per square foot. To the nearest dollar, how much will it cost to cover the garden with mulch?

27.5

Step-by-step explanation:

Use compound interest formula  F=P(1+i)^n twice, one for each deposit and sum the two results.

For the P=$40,000 deposit,
i=10%/2=5%  (semi-annual)
number of periods (6 months), n = 6*2 = 12
Future value (at end of year 6),
F = P(1+i)^n = 40,000(1+0.05)^12 = $71834.253

For the P=20000, deposited at the START of the fourth year, which is the same as the end of the third year.
i=5% (semi-annual
n=2*(6-3), n = 6 
Future value (at end of year 6)
F=P(1+i)^n = 20000(1+0.05)^6 = 26801.913

Total amount after 6 years
= 71834.253 + 26801.913
=98636.17   (to the nearest cent.)