In this task, you need to answer the given multiple-choice question on the gain. Gain is the value by which to multiply the input. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

[EX Q]: Problem: in a certain math department , students are required to enroll in either calculus or trigonometry , each of which is offered in beginner and advanced courses . the number of students enrolled in trigonometry is 50 % greater than the number of students enrolled in calculus , and 80 % of calculus students are enrolled in the beginner course . if 4 / 5 of students are in the beginner courses , and one student is selected at random , what is the probability that an advanced trigonometry student is selected ? 
Options: a ) 8 % , b ) 12 % , c ) 16 % , d ) 20 % , e ) 24 %
[EX A]: b

[EX Q]: Problem: a glass was filled with 40 ounces of water , and 0.01 ounce of the water evaporated each day during a 20 - day period . what percent of the original amount of water evaporated during this period ? 
Options: a ) 0.005 % , b ) 0.02 % , c ) 0.5 % , d ) 5 % , e ) 20 %
[EX A]: c

[EX Q]: Problem: what is the rate percent when the simple interest on rs . 900 amount to rs . 160 in 4 years ? 
Options: a ) 4.44 , b ) 5.44 , c ) 6.44 , d ) 7.44 , e ) 8.44
[EX A]:
a