$2($b$)\_$#$3$: A gas is compressed polytropically in a piston$-$cylinder assembly from $1\mathrm{.}01$atm,$70F$

to $4\mathrm{.}2$ atm $.$ Determine the work and change in internal energy, in Btu$/$lb$,$ for the following cases

using only data from Tables A$-22$E and A$-23$E$.$

a$)$ Air, $T_2=295F$

b$)$ Oxygen, $n=1\mathrm{.}24$

$2($b$)$#$3$ using the

assumption of constant specific heat values. Determine the percent error in these

approximations, assuming that the actual values are $38\mathrm{.}79Bt\frac{u}{l}b$ and $26\mathrm{.}79Bt\frac{u}{l}b,$ respectively.