The lines grew smaller on the stark, white wall, till they could not be read by any eyes at all. And the old optometrist, tired eyes, hair gray, said, “See, son. I told you this would all be yours one day.” And he took one last look around.

“Son,” said he, “I know you did well in optometry school. And I don’t mean to suggest that you’re anyone’s fool. But do you know when it comes to fitting glasses and lenses, how to charge for your services and reduce your expenses?” And the son shook his head and looked down.

“Don’t feel bad, son. Making a profit is one of your aims, so first cover the cost of your glasses and frames. Let’s say the combined cost is two hundred dollars; you say, two fifty and see if he hollers.” The son smiled and said, “Thank you, Dad.”

“If he winces and moans, son, say, ‘thanks,’ and pass, but if he’s still smiling, you say, ‘That’s for the glass.’ Add another two-fifty, it’s that plain and simple, and if he’s still smiling, say, ‘For the right temple.’” And the son proved to be a successful lad.