You are given a math word problem and you are supposed to make use of mathematical concepts like probability, combinatorics, linear equations, sequences/series, or simple operators like addition, subtraction, division, or multiplication to answer the given question. Choose the best option from the 5 given options and report that option.

[EX Q]: Question: What does the hexa number E78 in radix 7.

 Option A: 12455

 Option B: 14153

 Option C: 14256

 Option D: 13541

 Option E: 14541
[EX A]: Option D

[EX Q]: Question: The average of first seven prime numbers which are between 30 and 70 is

 Option A: 35.4

 Option B: 42

 Option C: 44.4

 Option D: 57

 Option E: 67
[EX A]: Option C

[EX Q]: Question: A man purchased a cow for Rs. 3000 and sold it the same day for Rs. 3600, allowing the buyer a credit of 2 years. If the rate of interest be 10% per annum, then the man has a gain of:

 Option A: 0%

 Option B: 1%

 Option C: 2%

 Option D: 3%

 Option E: 4%
[EX A]:
Option A