Which of the following statements are true? Select one: a. A manager of a standard expense center is responsible for total expenses incurred by the center regardless of the volume of output. b. A manager of a discretionary expense center ordinarily receives a fixed budget, negotiated with senior management but not linked to any units of output. c. Managers of both standard and discretionary expense centers routinely prepare flexible budgets. d. Managers of both standard and discretionary expense centers have little to no control over revenues. e. B and D