Using the appropriate tables, determine the change in specific entropy between the specified states, in Btu$/$lb $R.$

$($a$)$ water, $p_1=10lb\frac{f}{i}n.{?}^2,$ saturated vapor; $p_2=500lb\frac{f}{i}n.{?}^2,T_2=1000F.$

$($b$)$ ammonia, $p_1=140lb\frac{f}{i}n.{?}^2,T_1=160F$;$T_2=-10F,h_2=345Bt\frac{u}{l}b.$

$($c$)$ air as an ideal gas, $T_1=80F,p_1=1$atm;$T_2=340F,p=25$atm.

$($d$)$ oxygen as an ideal gas, $T_1=T_2=520R,p_1=10$atm,$p_2=9$atm.