VDOM and guaranteed bandwidth

Hello ,

We have a fortigate 301E and we have 3 VDOMs. Connected to the firewall is a 30Mbps link. Now we want to share the 30Mbps equally among the 3 different VDOM( 10Mbps guaranteed per VDOM) and allow them to use the unused bandwidth when possible (in the case a customer is not using his allocated 10Mbps).

Is this possible?

If yes , where should this setting be configured? Per VDOM or on ROOT?