Sparky Ltd is a business that employs a number of electricians. The business undertakes a range of work for its customers, from replacing fuses to installing complete wiring systems in new houses.

In respect of a particular job done by Sparky Ltd, into which category (direct or indirect) would each of the following cost elements fall?

The wages of the electrician who did the job;
Depreciation of the tools used by the electrician;
The cost of cable and other materials used on the job; and
Rent of the building where Sparky Ltd stores its inventories of cable and other materials.