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 reduction of 20% in the price of salt enables a lady to obtain 10kgs more for Rs.100, find the original price per kg?

 Option A: Rs.2.9

 Option B: Rs.2.1

 Option C: Rs.2.5

 Option D: Rs.2.2

 Option E: Rs.2.7
[EX A]: Option C

[EX Q]: Question: A board of length L feet is cut into two pieces such that the length of piece A is 4 feet less than three times the length of piece B. Which of the following is the length, in feet, of piece A?

 Option A: (L+4

 Option B: (L-4

 Option C: (3L-4

 Option D: (3L-1

 Option E: (3L+4
[EX A]: Option C

[EX Q]: Question: Mike drives his new Corvette from San Francisco to Las Vegas, a journey of 640 miles. He drives the first half of the trip at an average rate of 80 miles per hour, but has to slow down for the second half of his journey. If the second half of the trip takes him 200 percent longer than the first half, what is his average rate J in miles per hour for the entire trip?

 Option A: 26.7

 Option B: J=30.0

 Option C: J=40.0

 Option D: J=53.3

 Option E: 60
[EX A]:
Option C