4 dozen bagels cost $30.00. how much change will you receive if you pay for a dozen bagels with a ten dollar bill

Lets calculate how much is a dozen bagels, if 4 cost $30 then, each is:

eachBagel = 30/4 = $7.50

now you pay $7.50 with a $10 bill, so you receive $2.50 the remainder of the subtraction

Wait. But a dozen bagels would be 90 dollars. How would you pay if you have only a ten dollar bill?