Write the formula you would use to determine each amount.
a) What principal invested at 5% simple interest per year will earn $100 in interest at the end of 2 years?
b) What interest rate will allow $2000 to earn $120 interest in 2 years?
c) How much time will you need to invest $1000 at a rate of 1% per year to earn $100 in interest?
d) None of the above