Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.

[EX Q]: Problem: in a group of 100 people, 90 have an age of more 30 years, and the others have an age of less than 20 years. if a person is selected at random from this group, what is the probability the person ' s age is less than 20 ?
Options: a. 0.1, b. 0.55, c. 0.65, d. 0.75, e. 0.85
[EX A]: a

[EX Q]: Problem: there are 15 boys and 10 girls in a class. if three students are selected at random, in how many ways that 1 girl or 2 boys are selected ?
Options: a. 100, b. 105, c. 115, d. 120, e. 125
[EX A]: c

[EX Q]: Problem: a trader bought a car at 10 % discount on its original price. he sold it at a 80 % increase on the price he bought it. what percent of profit did he make on the original price ?
Options: a. 17 %, b. 62 %, c. 12 %, d. 19 %, e. 22 %
[EX A]:
b