Final answer:
Mark is performing a sensitivity analysis, which is a financial decision-making tool used to assess the impact of variable cost changes on a project's NPV.
Step-by-step explanation:
Mark is conducting a sensitivity analysis to determine how changes in the variable costs per unit would affect the project's net present value (NPV). Sensitivity analysis is a decision-making tool used in finance to model the impact of different variables on a particular outcome, in this case, the NPV of a project.
By changing the variable costs per unit within the analysis, Mark can understand how sensitive the NPV is to this particular change. This helps in decision-making by allowing a better grasp of potential risks associated with cost fluctuations.