While working alone at their constant rates computer x can process 240 files in 4 hours, and comp y 240 files in 8 hrs. if all files processed by these comp. are the same size how long would it take the two comp. working at the same time at their respective constant rates , to process a total of 240 files?
a. 2hrs
b. 2hrs 20 min
c. 2hrs 40 min
d. 6hrs
e. 6hrs 20 min