Difference between anger and exasperation

Little Ernie was having a problem with his homework.
?Dad,? he asked, ?What is the difference between ?anger? and ?exasperation???
?Well, son,? said his father, ?I?ll give you a practical demonstration.?
His father picked up the phone and dialled a number.
?Hello,? said a voice at the other end.
?Hello,? said Ernie?s father. ?Is Melvin there??
?There is no one called Melvin here!? the voice replied. ?Why don?t you look
up numbers before you dial them??
?You see?? said Ernie?s father. ?That man was not at all happy with our call.
But watch this!?
He then dialled the number again, and says, ?Hello, is Melvin there??
?Now look here!? the voice said angrily. ?I told you there is no Melvin here!
You have got a lot of nerve calling again!?
?Did you hear that?? Ernie?s father asked. ?That was ?anger?. Now, I will show
you what ?exasperation? is!?
He dialled once again. And on hearing the voice at the other end, Ernie?s
father said: ?Hello! This is Melvin. Have there been any calls for me??