(1) ∫fdx = [a(x-xx/40)] (0<x<20) = 10a = 1 ∴ a= 1/10
(2) ∫xf dx = [0.1(xx/2-xxx/60)] (0<x<20) = 0.1(200-400/3) = 20/3
(3) F(10) = 0.75, F(15) = 0.9375 ∴1000x0.75 + 1120x0.1875 + 1280x0.0625 = 1040
(1) ∫fdx = [a(x-xx/40)] (0<x<20) = 10a = 1 ∴ a= 1/10
(2) ∫xf dx = [0.1(xx/2-xxx/60)] (0<x<20) = 0.1(200-400/3) = 20/3
(3) F(10) = 0.75, F(15) = 0.9375 ∴1000x0.75 + 1120x0.1875 + 1280x0.0625 = 1040