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: (3x + 1) (2x - 5) = ax^2 + kx + n . What is the value of a - n + k ?

 Option A: 5

 Option B: 8

 Option C: 9

 Option D: 14

 Option E: 11

A: Option D
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Q: Question: A coin is tossed two times. What is the probability that there is at the least one tail?

 Option A: 3/4

 Option B: 31/37

 Option C: 31/18

 Option D: 31/10

 Option E: 31/19

A: Option A
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Q: Question: There are 20cm, 21cm, 22cm,23cm, 24cm,25cm rods of quantities 2,3,6,4,3,2 respectively. Find average of this data.

 Option A: 32.25

 Option B: 21.45

 Option C: 45

 Option D: 22.45

 Option E: 22

A:
Option D
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