Agrass starts with 30,000 kj of energy. how much energy would a cheetah acquire after it ate a zebra that consumed the grass?

In every trophic level, only 10% of energy is passed on.
Grass, with 30,000 kJ of energy, is eaten by a zebra.
Zebra then has 10% of 30,000 kJ from the grass, which is 3,000 kJ of energy.
Cheetah then eats the zebra, gaining only 10% of 3,000 kJ of energy of the zebra. Finally as conclusion, cheetah has 300 kJ of energy after having acquired the zebra.

The correct answer is b