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 person crosses a 800 m long street in 5 minutes. what is his speed in km per hour ?
Options: a. 1.23, b. 2.86, c. 4.36, d. 9.25, e. 9.61
e

Problem: one side of a rectangular field is 14 m and one of its diagonal is 17 m. find the area of the field.
Options: a. 134.4, b. 120, c. 150, d. 180, e. none
a

Problem: the speed of a car is 85 km in the first hour and 45 km in the second hour. what is the average speed of the car ?
Options: a. 72 kmph, b. 65 kmph, c. 30 kmph, d. 80 kmph, e. 82 kmph
b