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.

Q: Question: A certain number of workers can do a work in 85 days. If there were 10 workers more it could be finished in 10 days less. How many workers are there?

 Option A: 75

 Option B: 30

 Option C: 28

 Option D: 24

 Option E: 32

A: Option A
****
Q: Question: A bus takes 3 hours to cover a distance of 500 Km. how much should the speed in Kmph be maintained to cover the same direction in 5/3th of the previous time?

 Option A: 75 Kmph

 Option B: 100 Kmph

 Option C: 90 Kmph

 Option D: 65 Kmph

 Option E: 70 Kmph

A: Option B
****
Q: Question: In a certain boys camp, 20% of the total boys are from school A and 30% of those study science. If there are 42 boys in the camp that are from school A but do not study science then what is the total number of boys in the camp?

 Option A: 70

 Option B: 245

 Option C: 150

 Option D: 300

 Option E: 350

A:
Option D
****