Microwave

A blonde walks into an appliance store and says to the clerk :
- I want to buy that TV over there.
He says in return :
- I'm sorry, we don't sell stuff to blondes.
The next day, she comes in with red hair and says :
- I want to buy that TV over there.
He says :
- I'm sorry, we don't sell things to blondes.
The next day, she comes in with brown hair and says :
- I want to buy that TV over there.
He says :
- I'm sorry, we don't sell things to blondes.
Frustrated, she says :
- How do you know I’m a blonde ?
He replies :
- That's not a TV. It's a microwave.