Consider the infinite series sigma ^infinity _k = 1 1/7^k a. find the first four terms of the sequence of partial sums. b. use the results of part (a) to propose a formula for s_n. c. propose a value of the series. a. find the first four terms of the sequence of partial sums. s_1 =, s_2 =, s_3 =, s_4 = (simplify your answers.) b. use the results of part (a) to propose a formula for s_n. a. s_n = 7^n - 1/6 middot 7^n b. s_n = 7n/7^n c. s_n = n/7^n d. s_n = 6 middot 7^n/7^n - 1 c. propose a value of the series. a reasonable conjecture for the value of the series is