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 certain electric-company plan offers customers reduced rates for electricity used between 8 p.m. and 8 a.m. weekdays and 24 hours a day Saturdays and Sundays. Under this plan, the reduced rates Z apply to what fraction of a week?

 Option A:  1/2

 Option B:  5/8

 Option C:  9/14

 Option D:  16/21

 Option E:  9/10
[EX A]: Option C

[EX Q]: Question: Three number are in the ratio 5:6:7. The sum of its largest and smallest numbers equals the sum of the third number and 48. Find the third number?

 Option A: 87

 Option B: 57

 Option C: 48

 Option D: 26

 Option E: 28
[EX A]: Option C

[EX Q]: Question: If logX/(a2 + ab + b2) = log Y/(b2 + bc + c2) = logZ/(c2 + ca + a2), then Xa - b.Yb - c. Zc - a =?

 Option A: 0

 Option B: -1

 Option C: 1

 Option D: 2

 Option E: 3
[EX A]:
Option C