The compound interest formula is A = P(1 + i)", where A is the amount of money at the end of the investment; P is the principal amount deposited; i is the interest rate per compounding period, expressed as a decimal, and n is the number of compounding periods. An investment of $2 000 earns 6.5% per year, compounded quarterly. The number of compounding periods the money must be in the account before it increases in value to $20 000 is State your answer as a whole number