"On the Job" joke

In a company there are two employees, Jack and Jill. Both have been model
employees and have been much valued by the firm. However, due to financial
setbacks, the company is forced to let one of them go. But which one?
The boss decides on a plan. He will watch Jack closely for one day,
monitoring his performance. The next day, he will similarly scrutinize
Jill. Then he will announce which one he is going to keep and which one
will have to be fired.
The first day, Jack comes in early. He works hard all morning, not even
taking a coffee break. He skips lunch. He works hard all afternoon,
doesn't spend any time on the phone, and leaves late.
Noticing this, the boss begins to think, "If they're both such diligent
workers, the choice is going to be even harder."
The next day, Jill comes in late, complaining of a headache. She takes some
aspirin and hangs out at the water fountain talking to her friends. She
takes an extra long coffee break. She leaves early for lunch, and comes
back late. She's unproductive in the afternoon, spending much of her time
calling her friends and telling them how miserable she feels. She takes
some more aspirin and leaves early.
The boss takes note of this. His mind is made up.
So the next day, the boss calls Jill into his office. He tells her, "Jill,
I am afraid I either have to lay you or Jack off."
And she replies, "Well, you're going to have to jack off because I've got
a headache."