One mole of ideal gas is confined in a piston-cylinder device, which is 1 foot in diameter. The piston can be assumed weightless and frictionless. The internal and external pressures are both initially 1 atm. An additional weight of 10 lb_m is placed on top of the piston, and the piston drops until the gas pressure balances the force pushing the piston downward. The temperature of the gas is maintained at a constant temperature of 80°F throughout the process.

A. What is the final pressure of the gas?

B. What is the final volume of the gas? 

C. How much work was done on the gas during the process?