A grocer has a sale of Rs. 800, Rs. 900, Rs. 1000, Rs. 700 and Rs. 800 for 5 consecutive months. How much sale must he have in the sixth month so that he gets an average sale of Rs. 850? Pick one:
A) s . 440	B) s . 850	C) s . 450	D) s . 900	E) s . 950

Rationale: "total sale for 5 months = rs . ( 800 + 900 + 1000 + 700 + 800 ) = rs . 4200 required sale = rs . [ ( 850 x 6 ) - 4200 ] = rs . ( 5100 - 4200 ) = rs . 900 . option d"
Answer: D