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.

Problem: a sells a bicycle to b and makes a profit of 50 %. b sells the same bicycle to c at a profit of 25 %. if the final s. p. of the bicycle was rs. 225, find out the cost price of the bicycle for a.
Options: a. 237, b. 126, c. 971, d. 611, e. 120
e

Problem: 10, 1000, 100000, 10000000....
Options: a. 100, 000,000, b. 1,000, 000,000, c. 1, 000,000, 000,000, d. 100, e. 1, 000,000
b

Problem: the ratio, by volume, of soap to alcohol to water in a certain solution is 6: 30: 90. the solution will be altered so that the ratio of soap to alcohol is doubled while the ratio of soap to water is halved. if the altered solution will contain 150 cubic centimeters of alcohol, how many cubic centimeters of water will it contain ?
Options: a. 1200, b. 1300, c. 1500, d. 1800, e. 1900

d