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 rhombus has area 432 sq m, one diagonal is 36 cm. find other diagonal ?
Options: ['a. 2400 m', 'b. 2500 m', 'c. 2600 m', 'd. 2700 m', 'e. 2900 m']
a

Problem: ages of two persons differ by 20 years. if 6 year ago, the elder one be 3 times as old the younger one, find their present age
Options: a. 12,28, b. 14,30, c. 16,36, d. 18,34, e. 19,34
c

Problem: an aeroplane covers a certain distance of 670 kmph in 6 hours. to cover the same distance in 6 1 / 4 hours, it must travel at a speed of
Options: a. 440, b. 540, c. 643, d. 740, e. 250

c