A firm manufactures a product using two inputs (x and y) and has the following cost function:
Cost = f(x,y) = 35x2 + 2xy + 10y2 - 200x - 100y.
The firm may use any combination of the inputs x and y so long as x + y = 100. Find the amount of x and y that should be used to minimize cost while satisfying the restriction that x + y = 100. In addition, what is the minimum cost and SP for the constraint?