Rock Bottom Golf is an online golf equipment retailer that sells clubs, shoes, balls, and other golfing equipment. Rock Bottom's regular prices are lower than most competitors, but they go even lower with limited-time promotional pricing, especially around major holidays. For example, the Father's Day promotion offers $50 to $75 off Rock Bottom's already-low price on select clubs and range finders that normally cost hundreds of dollars. One current offer is $100 off the Tour Edge E529 Driver that Rock Bottom normally sells for $399.99. To get the word out about the offer, Rock Bottom spent $15,000 on banner ads on golf-related websites like golfchannel.com and pga.com. Rock Bottom understands that promotional pricing cuts into its profits for each sale but also knows that such time limited pricing generates excitement and a sense of urgency among buyers. In fact, Rock Bottom's research of past Father's Day promotions shows that shoppers are mostly men buying the clubs and gadgets for themselves!

How many additional drivers must Rock Bottom sell to break even on this promotion? Assume the $15,000 spent on banner ads is the only fixed cost associated with this promotion.