The Opportunity Cost of Investing in a New Lithotripter a Machine

The opportunity cost of investing in a new lithotripter a machine that pulverizes kidney stones with sound waves) is

A) defined by the dollar cost of the equipment.
B) the same for every health care provider.
C) measured by the difference between the expected revenues from selling the services of the lithotripter and the invoice cost of the machine.
D) defined by the next best use of the money invested in the equipment.
E) impossible to calculate.