The owner of a company wanted to purchase a new machine for his factory. He found three types of machines:
1-The first machine works 30 Minutes then stops to cool down for 5 Minute and works again another 30 Minutes and so on.
2-The second machine works 60 minutes then stops for 10 Minutes to cool down and so on.
3-The third machine works 90 minutes takes 15 minutes to cool down and so on.
If each product needs 30 minutes to be completely finished by any machine and the machine could work only 8.5 hours per day, which machine should he buy and why?