Mr. Green uses a linear function to estimate how installing solar panels on the roof of his house will reduce his electric bill. Mr. Green does not have any solar panels yet, and his electric bill is $133 per month on average. For each 100 square feet of solar panels he installs, Mr. Green's monthly electric bill will decrease by $13.50. How many square feet of solar panels must Mr. Green install to reduce his monthly electric bill to $25?

a) 800
b) 850
c) 900
d) 950