Urgent request - how much tip for Nepal porter and guide?

Hi, I know there is an International forum but it doesn't get much traffic and I need a quick answer so I hope it is OK to post this here.
I am on a trek in Nepal for 12 days and myself and a friend are with one porter and one guide shared between us. The porter is carrying a combined maximum of 20kg of our luggage. The trip cost US$820 for each of us.
How much do we each need to tip the porter and guide?
Thanks.
I am on a trek in Nepal for 12 days and myself and a friend are with one porter and one guide shared between us. The porter is carrying a combined maximum of 20kg of our luggage. The trip cost US$820 for each of us.
How much do we each need to tip the porter and guide?
Thanks.