2.1.7 (a) In a series of 40 payments the first 10 payments are 10 cach, the second 10 payments are 20 each, the third ten payments are 30 each, and the final 10 payments are 40 each. The payments are equally spaced and the interest rate is 5% per payment period Find the accumulated value at the time of the final payment. (b) Show that the accumulated value of the series is equal to 10 Silos + Szlos + Solos + $70.05