Answer the following with complete solutions:

A survey was performed among people 65 years of age and older who underwent open-heart surgery. It was found that 30% of patients died within 90 days of the operation, whereas an additional 25% of those who survived 90 days died within 5 years after the operation. 2. What is the mortality incidence (per patient month) in patients receiving this operation in the first 90 days after the operation? (assume that 90 days = 3 months.) 3. Answer the same question as in #2 for the period from 90 days to 5 years after the operation.