First find out how much interest earned each month by multiplying .07 x 250.00 = 17.50.
Now Mr. Smith deposits 250.00 + 17.50(interest earned) = 267.50 per month
New monthly deposit is 267.50
(New monthly deposit) 267.50 x 39 (months) = 10,432.50
Mr. Smith will have 10,432.50 in the account after 39 months.