amaths ,differentiation

7.an open rectangular container with a square base is to have a capacity of 64 cm3. the cost of wall is $10 per m2 and the cost of the base is $20 per m2. what is the minimum cost of the container?

11.in the fig, A and D are two towns in the same side of the main road BC. A road APD is to be made to join A and D to the main road. where should the location of P be in order that the length of the road is its
smallest?

fig:
http://i364.photobucket.com/albums/oo87/davis1991411/fig-1.jpg