167. A rigid tank contains 20 lbm of air at 20 psia and 70°F. More air is added to the tank until

the pressure and temperature rise to 35 psia and 90°F, respectively. Determine the amount of

air added to the tank.

A. 11.73 lb B. 13.73 lb

C. 15.73 lb D. 17.73 lb