Thermodynamics-- gas problem?

I got stuck on my thermo homework this week, and don't have much time to devote to puzzling it out as I have a huge exam to study for this weekend! Can you explain how to solve this problem? A rigid tank contains 20 lbm of air at 50 psia and 80oF. The air is now heated until its pressure doubles. Determine:... show more I got stuck on my thermo homework this week, and don't have much time to devote to puzzling it out as I have a huge exam to study for this weekend! Can you explain how to solve this problem?

A rigid tank contains 20 lbm of air at 50 psia and 80oF. The air is now heated until its pressure doubles. Determine: (a) the volume of the tank and, (b) the amount of heat transfer.

(Answers: (a) 80 ft3, 1898 Btu

For this question I tried model this as an ideal gas (was I correct in doing so?) and was going to try to solve P1V=mRT1=P2V=mRT2, but I couldn't find T2. Am I even using the right relation here, and if so, how do I find T2?
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