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: a and b started a business in partnership investing rs. 20,000 and rs. 15,000 respectively. after 6 months, c joined them with rs. 20,000. whatwill be b ' s share in total profit of rs. 15,000 earned at the end of 2 years from the startingof the business ?
Options: a. s. 5,000, b. s. 4,500, c. s. 5,700, d. s. 6,500, e. s. 7,500
[EX A]: b

[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: an electrical appliances store sold this month 400 % more than the average of all the other months in the year. the sales total for this month was approximately what percent of total sales for this year ?
Options: a. 14 %, b. 21 %., c. 31 %., d. 37 %., e. 43 %.
[EX A]:
b