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: if julie rows 32 km upstream and 72 km down steam taking 4 hours each, then the speed of the stream
Options: a. 1.5 kmph, b. 0.5 kmph, c. 0.4 kmph, d. 1.6 kmph, e. 2.5 kmph
b

Problem: if the sides of a triangle are 26 cm, 24 cm and 15 cm, what is its area ?
Options: a. 120, b. 772, c. 180, d. 266, e. 2848
c

Problem: a bookseller has two display windows. she plans to display 3 new fiction books in the left window, and 3 new non - fiction books in the right window. assuming she can put the 4 fiction books in any order, and separately, the 3 non - fiction books in any order, how many total configurations will there be for the two display windows ?
Options: a. 24, b. 72, c. 144, d. 36, e. 420
d