Solve the following first-order partial differential equations (a) pq = u with u(0, y) = y, (b) p+q= pq with u(x,0) = ax where a is a constar 1. %3D 17 (c) xp + yq = u with u(s,1) = -2s where s is a parame (d) pq = xy with u(x, y) = -y at x= 0. !!