Can you help with part (c) of this calculus question

Suppose that the integral I = / f(x) dax can be represented by the following Riemann sum using right endpoints and n subintervals: An 16 16 + . . +1 16 - n n (a) Determine b. b = 4 (b) Determine f(x). f(x) = sqrt(16 - x^2) (c) Evaluate the integral by interpreting it in terms of areas. I =