We consider the function 9(x, y) = 2 + yt, and 9(x, y) = Vx + y' and the integral g(x, y)dA a) Estimate the integral J3 using a Riemann sum with m 2, n = 3 on the domain D = [0, 6] x [0, 2], choosing the lower left corner of each sub-rectangle as an evaluation point. Remember that m represents the number of subdivisions in x and n represents the number of subdivisions in y. Give a simplified exact answer, then a decimal approximation rounded to the nearest hundredth. b) Is the value found in a) an underestimation or an overestimation of the real value of J3? Justify your answer.