While obtaining a client's health history related to smoking cigarettes, the nurse plans to determine the client's smoking pack years. What information should the nurse obtain for this calculation? Select all that apply.

A. Number of years the client smoked. This is necessary to calculate pack years as it gives the duration of smoking. B. Client's current age. This is not directly needed for the calculation of pack years, although it might be relevant to overall health assessment. C. Packs of cigarettes smoked per day. This is necessary to calculate pack years as it gives the daily smoking quantity. D. Number of attempts to quit smoking. This information is important for understanding the client's history but not needed for calculating pack years. E. Age when the client started smoking. While this gives context, it is not needed for the calculation if the total number of years smoked is known. However, it could help calculate the number of years smoked if the current age is used and smoking start age is known.