Trade Builders is housed in a small office building which it owns. The natural gas line, which provides gas for heating the building, explodes, and the building is destroyed. As a result of having to rent and equip temporary office quarters for use while the building is being re-built, Trade Builders' operating expenses are much higher than normal during the period of reconstruction. This loss is covered under Trade Builders' (Search Chapter 1) a. builders risk/installation floater policy. b. equipment breakdown policy. c. commercial property insurance policy with extra expense coverage. d. contractors equipment policy