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'.

Problem: a man can row 5 kmph in still water . when the river is running at 2 kmph , it takes him 1 hour to row to a place and black . what is the total distance traveled by the man ? 
Options: a ) 5.75 , b ) 5.7 , c ) 5.76 , d ) 4.2 , e ) 5.71
d

Problem: if 20 typists can type 50 letters in 30 minutes , then how many letters will 40 typists working at the same rate complete in 1 hour ? 
Options: a ) 400 , b ) 500 , c ) 350 , d ) 250 , e ) 200
a

Problem: a can do a piece of work in 4 hours ; b and c together can do it in 2 hours , which a and c together can do it in 2 hours . how long will b alone take to do it ? 
Options: a ) 2 hours , b ) 3 hours , c ) 4 hours , d ) 5 hours , e ) 6 hours

c