一道算不对的数学题Prep2007E2-PS-181

The distributor of cases of a certain beverage charges $60 per case for orders of 1 to 5 cases, $50 per case for orders of 6 to 20 cases, and $45 per case for orders of more than 20 cases. If the distributor filled three orders, one for 3 cases of the beverage, one for 11 cases of the beverage, and one for 30 cases of the beverage, what was the total amount the distributor charged for the orders?

答案给的是 2080  但是我怎么算都是2280 来求证一下_(´ཀ`」 ∠)_

计算过程：

order 1: 3*60=180

order 2: 5*60+6*50=600

order 3: 5*60+15*50+10*45=1500

加起来=2280