5 A school principal wants to buy some book cases for the school library. She can choose between two types of book case. Type A costs $10 and it requires 0.6 m² of floor space
and holds 0.8 m' of books. Type B costs $20 and it requires 0.8 m² of floor space and
holds 1.2 m' of books. The maximum floor space available is 7.2 m² and the budget is
$140 (but the school would prefer to spend less). What number and type of book cases
should the principal buy to get the largest possible storage space for books?