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:
| Model | Origin | Type | Version | In Service | Notes |
| --- | --- | --- | --- | --- | --- |
| LARC-V | United States | Amphibious Support Vehicle | LARC-V | 5 | Most refurbished in 2006. |
| GKN Aquatrack | United Kingdom | Amphibious Support Vehicle | Aquatrack | 2 | Introduced in mid 1990s. Originally owned by the Office of Civil Defense but under PMC stewardship. |
| AM General HMMWV | United States | Light Utility Vehicle | M998A1\n\nM1038A1\n\nM1025A1 | - | Divided into several variants and series |
| Maxi-Ambulance | United States | Light Utility Vehicle | M997A2 | 4 | 150 delivered to AFP on November 2011, PMC received 50 units. |
| M939 truck | United States | Heavy Utility Vehicle | M923 | - | Several delivered to AFP in 2013, several units for the Marines. |
| M35 Truck | United States | 2 1/2-ton Utility Vehicle | M35 | - | Divided into several variants and series. More delivered in 2013. |
| M151 | United States | 1/4-ton Light Utility Vehicle and Weapons Carrier | Standard | - | In Service, several carrying M40 106mm recoilless rifle |
| Delta Mini Cruiser | Philippines | 1/4-ton Light Utility Vehicle | M1777 | - | Divided into several variants and series, including short and stretched utility and armed variants, and modified variants for specialized units. |
| Marine Multi-purpose Vehicle | Philippines | Light Utility Vehicle and Weapons Carrier | Standard | - | To replace the M151 MUTT, usually armed with an M40 106mm recoilless rifle, or as a cheaper alternative to the Humvee. |
| KM-50 Series | Republic of Korea | 5-ton Utility Vehicle | KM-500 | 12 | 155mm Artillery prime mover. 1st batch of 6 delivered 2012. |
| KM-45 Series | Republic of Korea | 1 1/2-ton Utility Vehicle | KM-450 | >50 | 3000 purchased by AFP on 2007, 1000 units shared by Navy/Marines and Air Force |
| KM-45 Series | Republic of Korea | Field Ambulance | KM-451 | 12 | 500 purchased by AFP in 2012, 200 went to the Marines. |
Question:
how many maxi-ambulance vehicles are in service?
Answer:
4