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 man ' s speed with the current is 18 km / hr and the speed of the current is 2.5 km / hr. the man ' s speed against the current is ?
Options: a. 10, b. 18, c. 50, d. 30, e. 40
[EX A]: b

[EX Q]: Problem: on her annual road trip to visit her family in seal beach, california, traci stopped to rest after she traveled 1 ⁄ 3 of the total distance and again after she traveled 1 ⁄ 4 of the distance remaining between her first stop and her destination. she then drove the remaining 300 miles and arrived safely at her destination. what was the total distance, in miles, from traci ’ s starting point to seal beach ?
Options: a. 600, b. 300, c. 350, d. 400, e. 550
[EX A]: a

[EX Q]: Problem: a solid metallic spherical ball of diameter 6 cm is melted and recast into a cone with diameter of the base as 12 cm. the height of the cone is :
Options: ['a. 8 cm', 'b. 6 cm', 'c. 4 cm', 'd. 3 cm', 'e. none']
[EX A]:
d