英文的导数数学题,
(1pt)Thetotalcost(indollars)ofproducingcoffeemachinesis
C(x)=1900+70x-0.7x^2
(A)Findtheexactcostofproducingthe21stmachine.
Exactcostof21stmachine=
(B)Usemarginalcosttoapproximatethecostofproducingthe21stmachine.
Approx.costof21stmachine=