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'.

Problem: what is the rate percent when the simple interest on rs . 800 amount to rs . 200 in 4 years ? 
Options: a ) 5 % , b ) 7 % , c ) 6.25 % , d ) 2 % , e ) 4 %
c

Problem: two boys starts from the same place walking at the rate of 5.5 kmph and 7.5 kmph respectively in the same direction . what time will they take to be 32 km apart ? 
Options: a ) 18 , b ) 16 , c ) 19 , d ) 15 , e ) 34
b

Problem: a tank is filled to one quarter of its capacity with a mixture consisting of water and sodium chloride . the proportion of sodium chloride in the tank is 40 % by volume and the capacity of the tank is 24 gallons . if the water evaporates from the tank at the rate of 0.5 gallons per hour , and the amount of sodium chloride stays the same , what will be the concentration of water in the mixture in 4 hours ? 
Options: a ) 40 % , b ) 44 % , c ) 48 % , d ) 52 % , e ) 56 %

a