Let f(x,y) = 100 + 10 x + 25y - x^(2) - 5y^(2)
a. Describe the cross sections of the surface z = f(x,y) produced by cutting it with the planes y = 0, y = 1, y = 2, and y = 3.
b. Describe the cross sections of the surface in the planes x = 0, x = 1, x = 2, and x = 3.
c. Describe the surface z = f(x,y)