Sammy's business has its ups and downs. Some years students buy more pizza than other years. Thus, Sammy makes the following contributions to his retirement fund: year 1 $5000, year 2 $4,000, year 3 $6,000, year 4 $3,500 and year 5 $7,000. The interest rate is 6%. How much is Sammy's retirement fund worth today? A. $22,597 B. $25,500 C. $21,318 D. $17,561