30 pens and 75 pencils were purchased for 510. If the average price of a pencil was 2.00, find the average price of a pen.
Choose the correct choice from the following answers.
A) 10
B) 11
C) 12
D) can not be determined
E) none of the above

Rationale: "since average price of a pencil = 2 ∴ price of 75 pencils = 150 ∴ price of 30 pens = ( 510 – 150 ) = 360 ∴ average price of a pen = 360 ⁄ 60 = 12 answer c"
Answer: C