Associate Shipping Carrier with Warehouse

Hi, how do you associate a shipping method with a warehouse? For instance, warehouse 1 only uses UPS while warehouse 2 only uses USPS. Any help on this is appreciated. Thanks.

I haven't looked at this in detail but I would guess this is not possible at the moment without some custom development.

What happends if a customer buy a item from warehouse a and an item warehouse b would there be two shipping charges?

Using other e-commerce platforms with drop shipping functionality that support this scenario, the user would be notified stating that each product is coming from a different warehouse. The user is then presented with the shipping methods supported by each warehouse so yes, the user would incur two different shipping charges.