The correct answer is 920IU of vitamin D.
International Unit (IU) is a unit of measurement used widely to quantify hormones, vitamins, blood products and several medications. It refers to the mass or volume of a substance but varies depending on the substance which is being measured and its biological activity.
Regarding Vitamin D, 1 microgram (μg) of vitamin D is equivalent to 40IU. Since 6 oz of baked salmon contains 23 μg of vitamin D, Andy's vitamin D intake will be 920IU (23 μg * 40IU = 920IU).