The Answer is (A).
A basic principle is:
Pressure = Force / Area
Therefore:
1500 psi = Force / [π (1.5)2/4] (the area of a circle = πd2/4)
1500 psi (1.76 in2) = Force
Force = 2640 lb (This force is acting on the piston)
Therefore:
Pressure = Force / Area
20,000 psi = 2640 lb / Area
Area = 2640 lb / 20,000 psi
Area = .132 in2