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: A can complete the job in 4 hours and B can complete the same job in 3 hours. A works for 1 hour and then B joins and both complete the job. What fraction of the job did B complete

 Option A: 1/7

 Option B: 3/10

 Option C: 1/2

 Option D: 5/6

 Option E: 8/9
[EX A]: Option A

[EX Q]: Question: If one-third of one-fourth of a number is 15, then three-tenth of that number is

 Option A: 35

 Option B: 36

 Option C: 45

 Option D: 54

 Option E: 57
[EX A]: Option D

[EX Q]: Question: Little John had $8.50. He spent $1.25 on sweets and gave to his two friends $1.20 and $2.20. How much money was left?

 Option A: $5.85

 Option B: $6.85

 Option C: $ 3.85

 Option D: $2.85

 Option E: $4.85
[EX A]:
Option C