Sloths eat relatively little, but of food that is very hard…

Sloths eat relatively little, but of food that is very hard to digest. They also move relatively little as well. If a sloth eats 100 Calories of leaves in a day, it might lose 50 Calories in its feces, use 40 Calories for metabolism, respiration and a little bit of movement, and the remaining 10 Calories for growing more sloth. Which is the correct choice of calculations to determine the production efficiency of this sloth?