A continuous random variable Y has a pdf of f(y)=6/171(y+y²) where y is defined from 1 to 4, which expression describes F(Y), the cumulative density function for Y:
a. F(Y)= [infinity]in for 1≤ y ≤ 4
b. F(Y) = 3(y²-1)/171+2(y³-1)/171 for 1≤ y ≤ 4
c. F(Y)=3y²/171+2y³/171for 1≤ y ≤ 4
d. F(Y)=6y²/171+6y³/171 for 15 y ≤ 4
e. F(Y)= 0 for 1≤ y ≤ 4