how do we limit the bandwidth for dfferent IP subnet

I have one cisco7606 router with FWSM card. We have virtually divided the FWSM with two context (one "context-dmz1" and "context-trusted",  here  "Context-dmz1" will used for inbound traffic and "context-trusted"  will use for outbound traffic. Right now we have two ISP and both are having 16 Mbps bandwidth. Now we want "context-dmz1" will get 4 Mbps fixed bandwidth from ISP1 and "context-trusted" was divided into two inside segments where one IP subnet will get remaining 8 mbps bandwidth from ISP1 and another subnet will get fixed 16 Mbps fixed bandwidth from ISP2. Following is brief details of our requirent:

Contexts: "context-dmz1", "context-trusted"
ISP : ISP1 (16 Mbps) and ISP2 (16 Mbps)
Context-dmz1: 4 Mbps fixed bandwidth from ISP1
context-trusted:
IP Subnet1: 8 Mbps fixed bandwidth from ISP1
IP Subnet2: 16 Mbps fixed bandwidth from ISP2

Please give us a urgent solution how will we configure the Cisco7606 router for bandwidth limiting for different IP subnet for differnt context / interfaces. I have attached the design for the requirement. My Cisco routers MSFC card is having 48 port gigabyte ethetnet port.