What is the right hand riemann sum approximation

Question

A function f is continuous on the closed interval [4,12] and differentiable on the open interval (4,12) and f has the values below. Using 4 subintervals, what is the right hand riemann sum approximation.

Values : (4,50) (6,50) (9,38) (11,30) (12,0)

Answer 1

R₄ = 50·2 + 38·3 + 30·2 + 0·1 = 274