I need help with the following problem: Consider the following table: X. 4 8 12 16 20 f(x)|. 35|34|32|28 4 (a) Use this data and a left-endpoint Riemann sum to estimate the integral: int 0 ^ 20 f(x)dx=______ (b) Use this data and a right-endpoint Riemann sum to estimate the integral: int 0 ^ 20 f(x)dx=______ (C) Find the average of the left and right-endpoint Riemann sums to estimate the integral: int 0 ^ 20 f(x)dx=_____