Task: Question Answering
Input (English): Problem: sarah is driving to the airport . after driving at 20 miles per hour for one hour , she realizes that if she continues at that same average rate she will be an hour late for her flight . she then travels 50 miles per hour for the rest of the trip , and arrives 30 minutes before her flight departs . how many miles did she drive in all ? 
Options: a ) 140 , b ) 175 , c ) 210 , d ) 70 , e ) 280
Output (English): d