1. A clothing business finds there is a linear relationship between the number of hats (X) it can sell and the price (P) it can charge per hat. Historical data shows that 1,500 hats can be sold at a price of $40, while 2,000 hats can be sold at a price of $30. Find a linear equation in the form P(X) = bX + a that gives the price (P) they can charge for (X) hats.

1. If they gave away the hats for free, how many hats will people take away?
2. How much must they reduce the price of the hats in order to sell an additional hat?
3. How many hats can be sold at a price of $25 per hat?