A certain molecule has f degrees of freedom. Show that an ideal gas consisting of such molecules

Question:

A certain molecule has f degrees of freedom. Show that an ideal gas consisting of such molecules has the following properties: (1) its total internal energy is fnRT / 2; (2) its molar specific heat at constant volume is fR / 2; (3) its molar specific heat at constant pressure is (f + 2) R /2; (4) its specific heat ratio is y = CP/CV = (f + 2)/f.