David invested $220 in a savings account that offers a 3% return on the investment. the value of david's investment will be at least $400 after a period of years. hint: use the formula a = p(1 + r)t, where a is the amount after t years, p is the amount invested, r is the rate of interest, and t is the time period. use a calculator to compute the answer, and round it off to the nearest year.