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: 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
Example Output: a

Example Input: Problem: what is the least number of square tiles required to pave the floor of a room 11 m 50 cm long and 1 m 50 cm broad ?
Options: a ) 724 , b ) 804 , c ) 69 , d ) 844 , e ) none
Example Output: c

Example Input: Problem: if a car had traveled 25 kmh faster than it actually did , the trip would have lasted 30 minutes less . if the car went exactly 75 km , at what speed did it travel ?
Options: a ) 30 kmh , b ) 40 kmh , c ) 45 kmh , d ) 50 kmh , e ) 55 kmh
Example Output:
d