"Dry Cleaners" joke

One day 2 irish men were walking down the street when one of them noticed a sign sayin
"Shirts 4.99"
"Suits 7.99"
the first irish man thouht this was clearly a bargain and told his friend told his friend to go in and by 40 of each but to be careful not to let the the shop no he was irish as the shop would not serve him.
the second irish man went in and asked for 40 shirts and 40 suits, but to his suprise the man behind the counter replied
"your irish we dont serve the irish"
the irish man tried at his best to convince the man he was not irish but kept getting the same respose
"your irish we dont serve the irish"
the irish man gave up trying and began to walk out of the shop but as he reached the door he asked the man if he could at least answer his question and the man saw no harm and listened to his question
"how did you know i was irish" said the irish man
the man behind the counter kindly replied
"this is a dry cleaners mate"