The total cost of producing 1 unit of a product is given by
C(x, y) = 30 + 0.5x2 + 30y - xy dollars
where x is the hourly labor rate and y is the cost per pound of raw materials. The current hourly rate is $25, and the raw materials cost $6 per pound. How will an increase of
(a) $1 per pound for the raw materials affect the total cost?
(b) $1 in the hourly labor rate affect the total cost?