The corner points of the feasible region for an LPP are (0, 10), (5, 5), (15, 15) and (0, 20). If the objective function is Z=px+qy; p, q >0, then the condition on p and q so that the maximum of Z occurs at (15, 15) and (0, 20) is :

p=q p=2q q=2p q=3p

q=3p