An employer is negotiating a first contract with a union. It has found two alternative provisions regarding job vacancies that could be included in the agreement:

$($a$)$ One provides that seniority will be the determining factor if the skill and ability of two contending employees is equal.

$($b$)$ One provides that the employee with the most seniority will be awarded the job provided he or she has sufficient ability to do the job. Decide which of the two provisions the employer should seek to have included in the collective agreement and explain why.