The old man takes the old lady to the doctor for a checkup.
The doctor wants to have some fun with the old man so
after the checkup he tells the old man that the problem is
serious the old ladies health is deteriorating
and the only cure is sex.
The old man says sex?
Yes, the doctor says sex you know.
How many times she must have sex?
The doctor says three times a week.
What days? the old man says.
Well, lets say Tuesday, Thursday and Saturday.
Well, doctor Tuesday and Thursday I can but,
on Saturday I have something to do,
I can't bring her to you.