Average of money that group of 4 friends pay for rent each month is $800.After one persons rent is increased by 25% the new mean is $850.What was original rent of friend whose rent is increased? Choose the correct answer:
A) 800  B) 900  C) 1000  D) 1100  E) 1200

Rationale: "0.25 x = 4 ( 850 - 800 ) 0.25 x = 200 x = 800 answer a"
Answer: A