When an elastic band is stretched a distance x, it exerts a restoring force whose magnitude is ax + bx^2 where a and b are constants. The work done by one person to stretch the rubber band from x = 0 to x = L is:
a. aL + 2bL^2
b. bL
c. aL^2/2 + bL^3/3
d. a + 2bL