If Emery has $1,700 to invest at 7% per year compounded monthly, how long will it be before he has $2,600? If the compounding is continuous, how long will it be? Solution formula for compound interest monthly: Amount = Principal[ 1+r/12]^(t*12) 2800 = 1700[ 1 +0.07/12]^12t 1.647 = 1.0058^12t take natural log on both sides: ln(1.647) = 12*ln(1.0058) t = 7.149 yrs Continous Compounding : Amount = Principal(e^rt) 2800 = 1700 e^(0.07t) ln(28/17) = 0.07t t = 7.128 years Option C.