Problem: one night a certain hotel rented 2 / 5 of its rooms , including 2 / 3 of their air conditioned rooms . if 3 / 5 of its rooms were air conditioned , what percent of the rooms that were not rented were air conditioned ? 
Options: a ) 20 % , b ) 25 % , c ) 33 % , d ) 36 % , e ) 40 %
c