Which of the Following Is True for Economic Spacing

Multiple Choice

Which of the following is true for economic spacing?

A) cost of trusses should be equal to twice the cost of purlins
B) cost of trusses should be equal to twice the cost of purlins minus cost of roof coverings
C) cost of trusses should be equal to the cost of purlins plus cost of roof coverings
D) cost of trusses should be equal to twice the cost of purlins plus cost of roof coverings