Consider the budget set for a consumer with income of 100 facing the following prices. The price for the first five units of good 1 is $10 (per unit). If the consumer buys more than five units, the price is $5 for any subsequent unit purchased. If the consumer buys 2 units of good 2 at a price of $10 a unit and is on her budget constraint, how many units of good 1 does she buy?