To maximize your utility you should purchase A and B in such amounts that: their marginal utilities are the same.
The benefits or the satisfaction that is derived by the consumption of any product refers to the utility of that product. Marginal utility refers to the satisfaction that is attained in consuming an additional unit of goods and services. It is the satisfaction or benefits that are attained using an additional unit of goods and services.
It helps in the determination of the quantity of goods and services that the consumers needs to consume. In the given scenario, the money income that is available for the purchase of the products A and B are limited. Hence the utility can be maximized by purchasing the products A and B in such amounts that their marginal utilities are the same.