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: two trains, one from howrah to patna and the other from patna to howrah, start simultaneously. after they meet, the trains reach their destinations after 10 hours and 8 hours respectively. the ratio of their speeds is
Options: a. 4: 9, b. 4: 3, c. 4: 12, d. 4: 8, e. 4: 5
[EX A]: e

[EX Q]: Problem: a bottle contains a certain solution. in the bottled solution, the ratio of water to soap is 3: 4, and the ratio of soap to salt is five times this ratio. the solution is poured into an open container, and after some time, the ratio of water to soap in the open container is halved by water evaporation. at that time, what is the ratio of water to salt in the solution ?
Options: a. 9: 32, b. 9: 30, c. 32: 9, d. 19: 32, e. 18: 30
[EX A]: a

[EX Q]: Problem: a train covers a distance of 100 km in 1 hour. if its speed is decreased by 10 km / hr, the time taken by the car to cover the same distance will be ?
Options: a. 1 hr, b. 1 hr 6 min, c. 50 min, d. 1 hr 30 min, e. 1 hr 45 min
[EX A]:
b