Subject: mathqa
Question: running at their respective constant rate , machine x takes 2 days longer to produce w widgets than machines y . at these rates , if the two machines together produce 5 w / 4 widgets in 3 days , how many days would it take machine x alone to produce 6 w widgets .
Option: 
A: 12
B: 36
C: 10
D: 4
Answer: B