Iguana Insurance allows its customers to pay their premiums in full, in four quarterly payments, or as twelve monthly payments. Iguana adds a surcharge of $3 per payment if the customers choose a mode...

Iguana Insurance allows its customers to pay their premiums in full, in four quarterly payments, or as twelve monthly payments. Iguana adds a surcharge of $3 per payment if the customers choose a mode other than annual payment. It offers a rebate of $1 per payment if the customers set up an automatic withdrawal plan with their bank. How might Iguana justify these surcharges and discounts?