Marnie McKay, MD$,$ is a psychiatrist who is in heavy demand. Even though she has raised her fees considerably during the past $5$ years, Dr$.$ McKay still cannot accommodate all the patients who wish to see her. McKay has conducted $7$ hours of appointments a day, $6$ days a week, for $46$ weeks a year. Her fee averages $$225$ per hour. Her variable costs are negligible and may be ignored for decision purposes. Ignore income taxes.

$1.$ McKay is weary of working a $6-$day week. She is considering taking every other Saturday off. What would be her annual income $($a$)$ if she worked every Saturday and $($b$)$ if she worked every other Saturday?

$2.$ What would be her opportunity cost for the year of not working every other Saturday?

$3.$ Assume that Dr$.$ McKay has definitely decided to take every other Saturday off. She loves to repair her sports car by doing the work herself. If she works on her car during half a Saturday when she otherwise would not see patients, what is her opportunity cost?