If a certain toy store's revenue in November was 2/5 of its revenue in December and its revenue in January was 1/2 of its revenue in November, then the store's revenue in December was how many times the average (arithmetic mean) of its revenues in November and January?  Select the correct option:
A) 1 / 4  B) 1 / 2  C) 10 / 3  D) 2  E) 4

Rationale: "n = 2 d / 5 j = n / 2 = d / 5 the average of november and january is ( n + j ) / 2 = 3 d / 5 / 2 = 3 d / 10 d is 10 / 3 times the average of november and january . the answer is c ."
Answer: C