According to the energy pyramid concept, only 10% of received energy is transferred to the next trophic level while 90% of the energy is lost as heat. As a result, only 10% is transformed into available biomatter that can be consumed by the species of the higher trophic level.
Corn is a producer that has 25,000 kcal available. If we assume that a mouse (first-order consumer) consumes corn grains, it receives 10% of the energy that equals 25,000 kcal × 10% = 2,500 kcal. If the python (second-order consumer) hunts the mouse, it will receive only 10% of the energy available in the mouse. This energy equals 2,500 kcal × 10% = 250 kcal.
Answer: 250 kcal