C = {\frac{5x}{12} | x \in N , x \le 3}

B = {2x - 1 | x \in N , x \le 5}

A = {\frac{x^2 - 1}{9} | x \in N , x \le 5}

F = {\frac{x + 5}{3^x} | x \in Z , -2 \le x \le 2}