In this task, you need to answer the given multiple-choice question on the general math. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.
--------
Question: Problem: a company produces on an average 4000 items per month for the first 3 months . how many items it must produce on an average per month over the next 9 months , to average of 4375 items per month over the whole ?
Options: a ) 4500 , b ) 4600 , c ) 4680 , d ) 4710 , e ) none

Answer: a

Question: Problem: if 12 : 8 : : x : 16 , then find the value of x
Options: a ) 18 , b ) 24 , c ) 28 , d ) 16 , e ) 20

Answer: b

Question: Problem: a sports equipment store sold ping pong rackets for a total of $ 686 . if the average ( arithmetic mean ) price of a pair of rackets is $ 9.8 , how many pairs were sold ?
Options: a ) 50 , b ) 100 , c ) 70 , d ) 500 , e ) 980

Answer:
c