Let R be the region in R inside the triangle with vertices (0, 0), (1, 3) and (3, 3). (a) Sketch the region R, labelling all points of interest. (b) Given the substitution g(x, y) = (y - x, y - 3x) =: (u, v), determine g( R) and sketch the region in u-v-coordinates. (c) Use the substitution g to express the integral X dx dy y + x in terms of u and v. You must include the limits of integration. Note: you should leave your answer in integral form