Find the approximate area under the curve of y = 3x by dividing the interval between x = 2 and x = 4 into (a) n = 5 subintervals (Ax = 0.4) and (b) n = 10 subintervals (Ax = 0.2) subintervals, and then adding up the areas of the inscribed rectangles. The height of each rectangle may be found by evaluating the function for the proper x-value. . . . (a) The area is approximately . (Type an integer or a decimal.)