i can not figure out the answer to b.

please help!

Complete the following table using Vanguard's data for the Vanguard 500 Index Fund Admiral Shares (VFIAX). Average annual returns as of 12/31/2019 500 Index Fund Adm S&P 500 Index (Benchmark) 1-year 31.46% 31.49% 3-year 15.23% 15,27% 5-year 11.66% 11.70% 10-year 13.52% 13.56% How many years would it take to quadruple $250,000 to $1 million if you use the "Rule of 72" and the above 10-year average annual return