A store had 235 MP3 players in the month of January. Every month, 30% of the MP3 players were sold and 50 new MP3 players were stocked in the store.

Which recursive function best represents the number of MP3 players in the store f(n) after n months?
a f(n) = 0.7 × f(n − 1) + 50, f(0) = 235, n > 0
b f(n) = 237 − 0.7 × f(n − 1) + 50, f(0) = 235, n > 0
c f(n) = 0.3 × f(n − 1) + 50, f(0) = 235, n > 0
d f(n) = 237 + 0.7 × f(n − 1) + 50, f(0) = 235, n > 0