How do I do this question? Thanks!

Problem 3(10 pts) Consider a seller who sells m different products. For product j, there are Bj units in inventory. There are n customers, each customer i is interested in buying a bundle of the product Si, where Si{1,,m} and is willing to pay a price vi for it. For each customer, the seller can only decide to accept his entire request Si or reject him. The objective of the seller is to maximize the revenue. (a). Formulate this problem as an integer program. (b). Consider the following example B1=1,B2=2,B3=3,S1={1,2},v1=2,S2={3}, v2 =1. S3={1,3},v3=3,S4={2,3},v4=2,S5={2},v5=2. What is the optimal solution to the LP and IP respectively? What is the integrality gap