First find how many ounces of fruit Bill will need total: 12 ounces/batch * 4 batches = <<12*4=48>>48 ounces
Then find how many cartons of blueberries Bill would need: 48 ounces / 6 ounces/carton = <<48/6=8>>8 cartons
Then multiply that number by the cost per carton to find the total cost of the blueberries: 8 cartons * $5/carton = $<<8*5=40>>40
Then find how many cartons of raspberries Bill would need: 48 ounces / 8 ounces/carton = <<48/8=6>>6 cartons
Then multiply that number by the cost per carton to find the total cost of the raspberries: 6 cartons * $3/carton = $<<6*3=18>>18
Then subtract the cost of the raspberries from the cost of the blueberries to find the difference: $40 - $18 = $<<40-18=22>>22
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