A baseball team plays in a stadium with a ticket price of $8. The average attendance is 22,000. When the price drops to $7, the average attendance rises to 25,000. Find the demand function P(x), where x is the number of spectators. (Assume that P(x) is linear.)

a) P(x)=−500x+27,500
b) P(x)=500x+22,000
c) P(x)=−500x+25,000
d) P(x)=500x+27,500