calculation of cost for non labour resources assigned to all the project.

Which software?

If your activities are on a five-day week, BUT your non-labour resources can only be hired by a seven-day week, then the simplest ways to incorporate the costs is to create a daily cost for the resource which is 7/5ths of the weekly cost. BUT If you then decide to work at the weekend there is a problem My choice would be to create WBS Summary activity or activities (whose duration is automatically calculated as the duration of the WBS) with Fixed Units per Time period as the duration type, a seven-day calendar, and all the non-labour resources are attached to those activities. This will do the correct calculations for non-labour costs.