Collapse of earth into underground mines, or subsidence, is a serious problem. In room-and-pillar and long-wall mines, columns of coal and other structures are used to support the ground above. Later in the mining process, they are often taken out. The mines are left to collapse.
We view overhead as two types of costs and define them as follows: Manufacturing overhead (also referred to as factory overhead, factory burden, and manufacturing support costs) refers to indirect factory-related costs that are incurred when a product is manufactured.
The distribution of manufacturing overhead costs to individual product unit, or production batches generally, requires a base or a cost driver, to which reference a rate, known as material burden rate applies. Material burden is the amount of manufacturing overhead costs that a unit of the base carries.