page+376+number+48+(Alexa

(Using left-hand approximation) ∫ from 1 to 5 = f(1)dx+f(2)dx+f(3)dx+f(4)dx= 12 ∫ from 4 to 5 = f(4)dx= 3.6 So, ∫ from 1 to 4 = f(1)dx+f(2)dx+f(3)dx = f(1)dx+f(2)dx=f(3)dx+f(4)dx-f(4)dx= 12-3.6 = 8.4