Vitamin C is a vitamin found in fruits and vegetables. It cannot be stored in our body. Why ?

Why cannot Vitamin C be stored in our body ?

A dietician wishes to mix two kinds of food X and Y in such a way that the mixture contains atleast 10 units of vitamin A, 12 units of vitamin B and 8 units of vitamin C. The vitamin contents of one kg food is given below : One kg of food X cost Rs. 16 and one kg of food Y costs Rs. 20. Find the least cost of the mixture which will produce the required diet ?