You can tell them that if they would have organised a party and their chefs were absent on the place and they have to prepare dis much of food by themselves and wid great efforts you prepare it. Now the people who are comin 2 party takes lot more food then dy need and wastes a huge amount of d food u prepared wid a great effort ... how will u feel ? .... And to the b question answer is .... u can guve d leftover to the poor people and try not to do dis again ....!!