Chapter 5.2, Problem 57E

Psychology. A psychologist uses two types of boxes when studying mice and rats. Each mouse spends $10$ minutes per day in box $A$ and $20$ minutes per day in box $B$. Each rat spends $20$ minutes per day in box $A$ and $10$ minutes per day in box $B$. The total minimum time available per day is $800$ minutes for box $A$ and $640$ minutes for box $B$. If $x$ is the number of mice used and $y$ the number of rats used, write a system of linear inequalities that indicates appropriate restrictions on $x$ and $y$. Find the set of feasible solutions graphically.