Consider the piston – cylinder apparatus shown in Figure P20.69. The bottom of the cylinder contains 2.00 kg of water at just under 100.0°C. The cylinder has a radius of r = 7.50 cm. The piston of mass m = 3.00 kg sits on the surface of the water. An electric heater in the cylinder base transfers energy into the water at a rate of 100 W. Assume the cylinder is much taller than shown in the figure, so we don’t need to be concerned about the piston reaching the top of the cylinder.