Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Union | Employee Group | Number of Employees | Contract Status |
| --- | --- | --- | --- |
| Air Line Pilots Association, International (ALPA) | Pilots | 2,871 | Amendable 4/1/2020 |
| Association of Flight Attendants (AFA) | Flight attendants | 5,815 | Amendable 12/17/2021 |
| International Association of Machinists and Aerospace Workers (IAM) (a) | Ramp service and stock clerks | 688 | Amendable 7/19/2018 |
| IAM | Clerical, office and passenger service | 4,506 | Amendable 1/1/2019 |
| Aircraft Mechanics Fraternal Association (AMFA) (a) | Mechanics, inspectors and cleaners | 725 | Amendable 10/17/2021 |
| Mexico Workers Association of Air Transport | Mexico airport personnel | 73 | Amendable 9/29/2019 |
| Transport Workers Union of America (TWU) | Dispatchers | 87 | Amendable 3/24/2019 |
Question:
How many IAM employees did the Alaska Airlines have in 2018?
Answer:
4,506