10. Hibernian Products, Inc. sponsors a postretirement plan providing health care benefits to employees who have completed at least 10 years service and are age 53 years or older at retirement. To date, the employees that have retired under the plan have an average age of 60. No employee has worked beyond age 65. Roger was hired when he was 46 years old. What is the attribution period for accruing Hibernian's expected postretirement health care benefit obligation to Roger?