Let f(x,y) = xcos(7y) and x = u2 + v6 andy = u u. (if (if (a) Calculate the primary derivatives E' 7y. (Use symbolic notation and fractions where needed.) a \\ a \\ (b) Use the Chain Rule to calculate %. Leave the answer in terms of both the dependent and the independent variables. (Use symbolic notation and fractions where needed.) 6 f ' (c) Evaluate gi at (u, v) = (5, 1) by determining (x, y) for (u, v) = (5, 1). (Use symbolic notation and fractions where needed.) if 6:) (u.v)=(5.1} _