HELP ME PLS I WILL GIVE BRAINLIEST
Judy is working at a retail store over the summer break. A customer buys a $50 shirt that is on sale for 20% off. Judy computes the discount, then adds sales tax of 10%, and tells the customer how much he owes. The customer insists that Judy first add the sales tax and then apply the discount. He is convinced that this way he will save more money because the discount amount will be larger.

Is the customer right?
pls explain how to do this, I am very confused!