A joint-cost function is defined implicitly by the equation c+c=26+qA16+qB2 where c denotes the total cost (in dollars) for producing qA units of product A and qB units of product B. (a) If qA=6 and qB=3, find the corresponding value of c. (b) Determine the marginal costs with respect to qA and qB when qA=6 and qB=3. (a) If qA=6 and qB=3, the corresponding value of c is (Simplify your answer.)