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: the area of a triangle is with base 18 m and height 6 m ?
Options: a. 88 m 2, b. 10 m 2, c. 66 m 2, d. 54 m 2, e. 31 m 2
d

Problem: the average weight of a group of persons increased from 48 kg to 51 kg, when two persons weighing 78 kg and 93 kg join the group. find the initial number of members in the group ?
Options: a. 87, b. 67, c. 23, d. 75, e. 25
c

Problem: in right triangle abc, ac is the hypotenuse. if ac is 35 and ab + bc = 55, what is the area of the triangle abc ?
Options: a. 225, b. 450, c. 25 √ 2, d. 200, e. 200 √ 2

b