17.8 stones
Though I doubt your ability to make stone, I do believe that you could mine and or cut an existing one and there are many such stones that I could not lift.
The difference between heavy lift surcharge and long lift surcharge is the size of the cargo. Long lift surcharges are applied when the length of the cargo exceed the rules. Heavy lift surcharge is when the weight of the cargo exceeds the going rate.
20 US stones is 250 pounds.
Lift is not a preposition. It is a verb as in Can you lift this heavy box? or, lift is a noun as in Can you give me a lift downtown?
Lift Heavy and eat healthy if you want to add muscle
Heavy as in blunt, no. Heavy as in hard to lift, yes!
because we can't lift it with our hand
That depends how high you want to lift it.
15 stone
79.8kg = 12.6st
34.57 stone