explain why this is a two sided market

A television channel wants to attract viewers and advertisers. There are 1000 potential viewers and 50 potential advertisers. Advertisers are willing to pay on the basis of the number of viewers of the tv channel. Demand from advertisers is downward sloping. At a price pA, the number of advertisements sold to advertisers equals qA = 50 - 10pA. Note that pA is the price that each advertiser has to pay per viewer. The total amount that each advertiser pays thus equals pA* qV, where qV is the number of viewers. Demand from viewers is downward sloping. At a price pV, the number of viewers equals qV = 1000- 200 pV. Viewers are willing to pay more if there are fewer advertisements in the television. One convenient way to model this market is to assume that viewers are willing to pay for the lack of advertisements. Potentially, there could be 50 advertisements in the newspaper. We assume that for every advertisement less than that, viewers have to pay the amount pV. The total amount that each reader pays thus equals pV * (50- qA). For simplicity, assume marginal costs are zero. A. Determine the profit-maximizing prices pA and pV, the number of viewers and advertisers, and the profits. B. Explain why this is a two-sided market