The cost C of manufacturing a certain
product can be estimated by the
formula C = 0.03rst2, where r and s
are the amounts, in pounds, of the two
major ingredients and t is the
production time in hours. If r is
increased by 50 percent, s is increased
by 20 percent, and t is decreased by
30 percent, by approximately what
percent will the estimated cost of
manufacturing the product change?
(A) 40% increase
(B) 12% increase
(C) 4% increase
(D) 12% decrease
(E) 24% decrease