One of the reasons why it is so difficult to calculate a current cost of manufacturing overhead is: Select one: a. All indirect costs respond to a single cost driver (cost driver) b. Regulatory bodies of the profession such as the FASB at the US level or the IASB at the global level establish clear standards for computing indirect cost. c. Indirect costs individually represent significant costs of the product or service d. Indirect costs as well as the level of activity vary, producing fluctuations in costs.