Find the missing number

Johnny wanted to have sex with a girl in his office,
But she belonged to someone else...
One day, Johnny got so frustrated that he went up to
her and said, "I'll give you a £100 if you let me
have sex with you. But the girl said NO.
Johnny said, "I'll be fast. I'll throw the money on
the floor, you bend down, and I'll be finished by the
time you pick it up. "
She thought for a moment and said that she would have
to consult her boyfriend... So she called her
boyfriend and told him the story.
Her boyfriend says, "Ask him for £200, pick up the
money very fast, he won't even be able to get his
Pants down."
So she agrees and accepts the proposal. Half an hour
goes by, and the boyfriend is waiting for his
girlfriend to call.
Finally, after 45 minutes, the boyfriend calls and
asks what happened.

She responded, "The bastard used coins!"