If he buys 2 bottles, the price drops to $20.00 per bottle so they cost 2*20 = $<<2*20=40.00>>40.00
He can get 80 loads of laundry per bottle and he bought 2 bottles so that's 80*2 = <<80*2=160>>160 loads of laundry
The detergent cost $40.00 and he will be able to wash 160 loads of laundry so each load costs 40/160 = $<<40/160=0.25>>0.25
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