Please help me answer these 4 questions.

7. The goal of this problem is to find the definite integral / x dx for any constant a > 0 as a limit of a Riemann sum. (a) Evaluate the Riemann sum S(n) = > f(ci)Axi in terms of n, by setting Xi = a and Ci = Xi, i= 1 where Axi = Xi - Xi-1. [Hint: (i - 1)3 = 13 - 312 + 3i - 1.] (b) Conclude by finding lim S(n) in terms of the constant a.6. Find constants a