Task: Question Answering
Input (English): Problem: points x , y , and z lie , in that order , on a straight railroad track . the distance from point x to point y is twice the distance from point y to point z . a train traveled from point x to point z without stopping . the train ' s average speed when traveling from point x to point y was 300 miles per hour and the train ' s average speed when traveling from point y to point z was 100 miles per hour . what was the train ' s average speed , in miles per hour , when traveling from point x to point z ? 
Options: a ) 200 , b ) 220 , c ) 240 , d ) 180 , e ) 260
Output (English): d