A 55-year-old female has been taking alprazolam 1 mg three times daily for 5 years for generalized anxiety disorder. She wants to discontinue the medication. The PMHNP plans to convert her to an equivalent dose of a longer-acting benzodiazepine to facilitate a gradual taper. Which of the following is the approximate diazepam equivalent of her total daily alprazolam dose and the rationale for this strategy?