A local sports bar routinely promotes sporting events, such as the Super Bowl, the NCAA Sweet Sixteen tournament, the BCS games, the Masters, NBA and NFL playoffs, NHL, baseball, NASCAR, and key curling bonspiels. By keeping records, the owner has determined that when the cover price is $13 the average number of patrons is 235. For every $1 change in cover charge, the number of patrons changes by 9. Assuming a linear demand curve, calculate the maximum willingness to buy for sporting events at this sports bar.

The correct answer is 352

Please explain how this is the correct answer? Thank you