Need step by step proof

5: Suppose that there are p companies and that the ith company sends mi representative to a conference. In this conference, there will be q work groups, each with at most n, participants. The organizers of the conference want a schedule that assigns each representative to exactly one group, but no group can contain two representatives from the same company. The groups do not have to be filled to capacity. Show how to use network flows to test whether the constraints can be satisfied. For this problem, you have to describe the network and how it can be used to test whether the constraints can be satisfied