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 cross - section of a cannel is a trapezium in shape. if the cannel is 12 m wide at the top and 2 m wide at the bottom and the area of cross - section is 4200 sq m, the depth of cannel is ?
Options: a. 500, b. 600, c. 700, d. 800, e. 900
b

Problem: a lady grows broccoli in her garden that is in the shape of a square. each broccoli takes 1 square foot of area in her garden. this year, she has increased her output by 79 broccoli when compared to last year. the shape of the area used for growing the broccoli has remained a square in both these years. how many broccoli did she produce this year ?
Options: ['a. 1600', 'b. 1500', 'c. 1650', 'd. 1700', 'e. can not be determined']
a

Problem: 5 % of ( 25 % of $ 1600 ) is ?
Options: a. $ 20, b. $ 30, c. $ 45, d. $ 15, e. $ 60
a