A copper (Young's modulus 1.1 x 1011 N/m2) cylinder and a brass (Young's modulus 9.0 x 1010 N/m2) cylinder are stacked end to end, as in the drawing. Each cylinder has a radius of 0.40 cm. A compressive force of F = 9800 N is applied to the right end of the brass cylinder. Find the amount by which the length of the stack decreases.