Parameters to deside no of plants

Hi friends

Can any one tell me the parameters to consider for deciding no of plants for client.

Ex: Client having one company and having 3 divisions .

1st division delas with trading Electorning good, Purchase as finished components and sale(Trading)

2nd division delas with Airconding trading. It also involves installationa at customer place. but no production facilty

3rd division : Power equipments . Purely purchase and sale and instalationa t client place.

All the 3 divison have office in same place. and have seperat purchase person.

wheterh we can go with one plant or 3 plants ? What are all the details to be considere on materila angle for above consideration

Rgds

Madhavan