Q: 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: walking with 4 / 5 of my usual speed , i miss the bus by 5 minutes . what is my usual time ?
Options: a ) 145 , b ) 5617 , c ) 15 , d ) 20 , e ) 12
A:
d