A full year has 12 months. So 2 years is 2*12 = <<2*12=24>>24 months
The loan amount is $6,000 that he will repay in 24 months so 6000/24 = $<<6000/24=250>>250 per month
If he paid his dad back in 5 years that 5*12 = <<5*12=60>>60 months
$6,000 loan spread out over 60 months is 6000/60 = $<<6000/60=100>>100 per month
To pay it off in 2 years instead of 5, Gary is paying 250-100 = $<<250-100=150>>150 more per month
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