If `C_(P_` and `C_(v)` denote the specific heats nitrogen per unite mass at constant pressure and constant volume respectively, then
(1) `C_(P)-C_(v)=(R)/(28)` (2) `C_(P)-C_(v)=(R)/(14)`
(3) `C_(P)-C_(v)=R` (4) `C_(P)-C_(v)=28R`