Hi could you expand on this? I don't understand how it's 3/5 and 7/20

The price of 1 gram is 5.90/250 = 0.02 0.02 * 700 = $14

Not sure if this is the way to do it but if you divide 150 by 2.5 you get 60. So maybe just divide 2.5 hours by 2.5 = 1 hour?