A piston$-$cylinder assembly $($see image below$)$ contains $2$ lb of air at a temperature of $540R$ and a pressure of $1$ atm $.$

The air is compressed to a state where the temperature is $840R$ and the pressure is $6$ atm $,$ illustrated in the following picture:

During the compression, there is a heat transfer from the air to the surroundings equal to $20$ Btu. Using the ideal gas model for air, determine the work during the process, in Btu.