Oohh, oohh - lemme give it a shot: The square root of ****-all!
I don't do metric, so had to convert to pounds (as all proper alberts are delivered - despite the RAF's decision to subrogate themselves to the movers whims) & using my pilot math (KG x 2 + 20%), I came up with round about 6K lbs which means very little in the grand scheme of things...
I assume you're trying to figure out your share of the petrol, eh? Charter air doesn't typically work that way. An easier way would be figure entire cargo weight by operating costs & then figure your percentage of the cargo weight (again, true charter cargo doesn't work this way, but close enough...)