(1) 总成本:C(x)=∫Cm(x)dx
=∫(2-x)dx
=2x-1/2x^2+C0
=-1/2x^2+2x+22
即:C(x)=-1/2x^2+2x+22
总收益:R(x)=∫Rm(x)dx
=∫(20-4x)dx
=20x-4*1/2x^2+R0
=-2x^2+20x (R0=0)
(2) 利润:L(x)=R(x)-C(x)
=-2x^2+20x-(-1/2x^2+2x+22)
=-3/2x^2+18x-22
=-3/2(x^2-12x+36)-22+3/2*36
=-3/2(x-6)^2+32
当利润获得最大值32万元时的产量为x=6百台
(3) x=6+4=10
L(x)=-3/2(10-6)^2+32
=-3/2*16+32
=8万元
再生产4百台,总利润由32万元降为8万元.