13. Consider the solid Q drawn in the first octant, as shown below, consisting of the surfaces x = (y -3) +1, 3x + 4z =15, x=1, y=1, z=0 2 If the point density of the solid is determined by the function p(x, y, z) = 2x kg/m^3 and if the scale of the axes is in meters, then the mass of the solid is approximately: A) 52.8134 kg B) 31.8857 kg C) 21.2571 kg D) 20.5710 kg 14. Consider z as a function of the variables x, and which is defined by Z = In(x5y8) + " and let P (-1, 1) be a point. Also consider the vectors u = (a, B), w = (a, -B), such that lull = V41 . If 48V41 32V41 Duz(P) = 41 y Du=(P) = 41 determine: The value of a: The value of B