Let C1 and C2 be the graph of the function y = x2 and y = 2x respectively. Let C3 be the graph of the function
y = f (x), 0 ≤ x ≤ 1, f (0) = 0. Consider a point P on C1. Let the lines through P, parallel to the axes meet C2 and C3 at Q and R respectively (see figure). If for every position of P (on C1) the area of the shaded regions OPQ and OPR are equal, determine the function f(x).

a) x2 – 1
b) x3 – 1
c) x3 – x2
d) 1 + x2 + x3