Calculate A+B

During a fire at a convent, a group of nuns are trapped on the third floor. Thinking quickly, they took off their habits, tied them together and used them as a rope to climb down from the window.After safely reaching the ground, a reporter asks, “Weren’t you worried that the habits would have ripped as you were climbing down? They look old and worn.”“Of course not!” said one of the nuns. “Don’t you know how hard it is to break an old habit?”