In this task, you need to answer the given multiple-choice question on the physics. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

[EX Q]: Problem: a swimmer can swim in still water at 4 km / h . if the speed of the water current is 2 km / h , how many hours will the swimmer take to swim against the current for 5 km ? 
Options: a ) 2.0 , b ) 2.5 , c ) 3.0 , d ) 3.5 , e ) 4.0
[EX A]: b

[EX Q]: Problem: the length of a room is 5.5 m and width is 3.75 m . what is the cost of paying the floor by slabs at the rate of $ 300 per sq . metre . 
Options: a ) $ 2587.50 , b ) $ 3587.50 , c ) $ 4187.50 , d ) $ 6187.50 , e ) $ 8587.50
[EX A]: d

[EX Q]: Problem: if a is thrice as fast as b and together can do a work in 15 days . in how many days a alone can do the work ? 
Options: a ) 36 , b ) 20 , c ) 28 , d ) 54 , e ) 45
[EX A]:
b