The cost of 3 pens and 5 pencils is Rs.200. Also the cost of one pen and one pencil is in the ratio of 5:1 respectively. What is the cost of one dozen pens?	Choose the correct choice:
A) rs . 200	B) rs . 250	C) rs . 300	D) rs . 150	E) rs . 600

Rationale: "explanation : let the cost of one pen is ‘ 5 x ’ and pencil is ‘ x ’ 3 x 5 x + 5 x = rs . 200 15 x + 5 x = rs . 200 x = 200 / 20 = 10 : . cost of 1 pen = 5 x = 5 x 10 = 50 : . cost of 12 pens , i . e . ( one dozen ) = 50 x 12 = rs . 600 answer : option e"
Answer: E