a. Food remains safe at 5oC because this temperature prevents the growth of microorganisms. Microorganisms usually require hot and humid places to grow whereas at this temperature they cannot grow and survive. Their metabolic activities are inhibited at this temperature.
b. Nowadays, foods are served in buffet style during large gatherings to prevent the wastage of food. Every indivisual can choose what to eat and how much to eat according to their wish and thus prevents the wastage of food.