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'.

Example Input: Problem: a constructor estimates that 3 people can paint mr khans house in 4 days . if he uses 4 people instead of 3 , how long will they take to complete the job ?
Options: a ) 2 , b ) 8 , c ) 1 , d ) 3 , e ) 4
Example Output: d

Example Input: Problem: two taps a and b can fill a cistern in 12 minutes and 18 minutes respectively . they are turned on at the same time . if the tap a is turned off after 4 minutes , how long will tap b take to fill the rest of the cistern ?
Options: a ) 8 min . , b ) 9 min . , c ) 10 min . , d ) 7 min . , e ) none of these
Example Output: a

Example Input: Problem: it takes printer a 4 more minutes more than printer b to print 40 pages . working together , the two printers can print 50 pages in 6 minutes . how long will it take printer a to print 140 pages ?
Options: a ) 12 , b ) 18 , c ) 20 , d ) 42 , e ) 30
Example Output:
d