Task: Question Answering
Input (English): Problem: a company has two models of computers , model x and model y . operating at a constant rate , a model x computer can complete a certain task in 60 minutes and a model y computer can complete the same task in 30 minutes . if the company used the same number of each model of computer to complete the task in 1 minute , how many model x computers were used ? 
Options: a ) 18 , b ) 16 , c ) 15 , d ) 17 , e ) 20
Output (English): e