In the days when a soda float costed less a 9 year old girl entered a coffee shop and sat at a table. A waiter put the menu in front of her. “How much is a soda float?” “One dollar,” replied the waiter.     The little girl pulled her hand out of her cute little pink purse and studied a number coins in it. “How much is a bottle of soda?” she inquired. Some people were now waiting for a table and the waiter was a bit impatient. “75 cents.” He said brusquely.     The little girl again counted the coins. “I’ll have a bottle of soda,” she said. The waiter brought the soda bottle, put the bill on the table and walked away. The girl finished the soda, paid the cashier and departed.     When the waiter returned, he began wiping down the table and then swallowed hard at what he saw. There, placed neatly beside the empty dish, were 25 cents – his tip.   Why did the waiter swallow hard?