A Store Is Offering a Discount on 800 Pairs of Basketball

A store is offering a discount on 800 pairs of basketball shoes. The amount of the discount varies and is not revealed to the customer until checkout. The distribution of discounts is given in the below table.
​ $$\begin{array} { | l | c | } \hline \text { Store Location } & \text { Potential Areas Covered } \\\hline \text { L1 } & 3,4,6,8 \\\hline \text { L2 } & 1,5,9 \\\hline \text { L3 } & 1,4,7 \\\hline \text { L4 } & 2,6,7 \\\hline \text { L5 } & 3,4,9 \\\hline \text { L6 } & 2,7,9 \\\hline \text { L7 } & 4,8,9 \\\hline \text { L8 } & 1,2,5,6 \\\hline \text { L9 } & 3,6,8 \\\hline\end{array}$$ ​
Formulate an integer programming model that could be used to find the minimum number of stores to open in order to cover customers of all areas for the home delivery service.