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: barbata invests $ 2200 in the national bank at 5 %. how much additional money must she invest at 8 % so that the total annual income will be equal to 6 % of her entire investment ?
Options: a. 1100, b. 3000, c. 1000, d. 3600, e. 2400
a

Problem: 40 is subtracted from 60 % of a number, the result is 50. find the number ?
Options: a. 150, b. 330, c. 277, d. 279, e. 712
a

Problem: a train of 30 carriages, each of 60 meters length, when an engine also of 60 meters length is running at a speed of 60 kmph. in what time will the train cross a bridge 1.5 km long ?
Options: a. 6, b. 3.3, c. 4, d. 9, e. 2

b