A very elderly couple were sat in their lounge at home facing each other and all was quiet.
The man suddenly stood up, walked across to his wife and slapped her hard across the face.
" What the hell's that for? " she asked"
"For giving me bad sex for 60 years ", he replied
Two hours later she stood up, walked across the room and slapped him harder across his face. " Why the hell have you done that ?" he asked.
She said " For knowing the difference".
