Breast cancer patients in a London, England, hospital were being treated for spinal metastases. They were followed over a five-year period, with their ambulatory state being recorded before treatment began, and at zero, three, and six months, one, two, and five years. Their ambulatory status, defined by whether or not they could walk unaided, is shown in Table 6.7.

(a) What are the probabilities of transition between the two ambulatory states?

(b) Do they evolve over time?

(c) What is the risk of death?