Answer:
OPPORTUNITY COST OF CAPITAL
Explanation: Opportunity cost of capital can be described as the incremental return a company foregoes when ever it is embarking on any internal investments.
The rule tries to show that a firm should only embark on projects or investment that will guarantee a higher rate of return after consideration of all the opportunity costs attached to the capital investment.
If the investment is a marketable security if the opportunity costs of capital is less than the expected rate of return,the investment is considering as a wrong choice.