A Gas-Filled Vertical Cylinder,closed at the Bottom End,is Fitted at the Top

Multiple Choice

A gas-filled vertical cylinder,closed at the bottom end,is fitted at the top with a piston that can move freely.The mass of the piston is 10.0 kg,and the initial height of the piston above the bottom of the cylinder is 25 cm.A mass of 8.0 kg is placed on the piston.What is the resulting height of the piston,assuming that the temperature of the ideal gas is kept constant?

A) 12 cm
B) 13 cm
C) 14 cm
D) 15 cm
E) 16 cm