Task: Question Answering
Input (English): Problem: the distance from city a to city b is 180 miles . while driving from city a to city b , bob drives at a constant speed of 40 miles per hour . alice leaves city a 30 minutes after bob . what is the minimum constant speed in miles per hour that alice must exceed in order to arrive in city b before bob ? 
Options: a ) 45 , b ) 48 , c ) 50 , d ) 52 , e ) 54
Output (English): a