For a VDI install??? If the guest OS is going to be Windows XP, then it's a 1:1 ratio. All 10 can get to the workstation, however only one at a time.
Depends on how many of the 10 work concurrently. If they want to work at the same time you'll need 10 VMs, but you can create 1 template and let the VDM create the VMs automatically from the template.
There are 10 types of people. Those who understand binary and the rest. And those who understand gray-code.