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: the speed of a boat in still water is 15 km / hr and the rate of current is 3 km / hr . the distance travelled downstream in 12 minutes is 
Options: a ) 1.2 km , b ) 1.8 km , c ) 2.4 km , d ) 3.6 km , e ) 1.6 km
Example Output: d

Example Input: Problem: today mary ’ s father is 4 times as old as mary . 3 years ago , he was 5 times as old . how old is mary today ? 
Options: a ) 6 , b ) 8 , c ) 10 , d ) 12 , e ) 14
Example Output: d

Example Input: Problem: a squirrel can climb 5 metres of a pole in one minute but slips 2 metres in the next minute . how much time will the squirrel take to climb 26 metres ? 
Options: a ) 15 minutes , b ) 18 minutes , c ) 12 minutes , d ) 58 minutes , e ) 10 minutes
Example Output:
a