Direct costs are incurred for the exclusive benefit of a project (for example, salary of the project manager, materials used by the project, and subcontractor expenses). Indirect costs, also called overhead costs, are allocated to a project by its performing organization as a cost of doing business. These costs cannot be traced to a specific project and are accumulated and allocated equitably over multiple projects (for example, security guards, fringe benefits, and electricity). Other examples of costs to estimate are cost of financing including any interest if needed, inflation allowance, exchange rates, or a contingency reserve. Costs are estimated for all resources to be charged to the project.