Demand function: At a price of $5 each, 300 hats will be sold. However, at a price of $3 each, 800 hats will be sold. How can the number of hats sold be expressed as a linear function of the price per hat?

A) 300 - 100x
B) 800 + 200x
C) 300 + 100x
D) 800 - 200x