Which of the following is the correct formula to calculate Return on Investment $($ROI$)?$

Question $9$ options:

$($the expected returns from a project $$ the cost implementing a project$)/$ the amount of time required to complete the project.

$($the cost implementing a project $-$ the expected returns from a project$)/$ the amount of time required to complete the project.

$($the cost implementing a project $-$ the amount of time required to complete the project$)/$ the expected returns from a project.

$($the expected returns from a project $-$ the amount of time required to complete the project$)/$ the cost implementing a project.