The Diamond Corporation provides its employees with a retirement benefit equal to 2% of salary for each year of service and the payout at retirement is based on the average salary for the last four years of employee service. This retirement benefit is fully vested after five years but does not vest before that time. The Diamond Corporation's retirement plan is aln) career average salary defined contribution plan with cliff vesting final average salary defined contribution plan with graded vesting final average salary defined benefit plan with cliff vesting career average salary defined benefit plan with graded vesting