If the grass in this example had 25,000 Kcal of energy,
approximately how much would you expect of that energy to
be stored in trophic level 4?

You would expect 25 Kcal of energy stored in trophic level 4.

Explanation:

Energy flow in the ecosystem follows 10% law according to which 10% of the energy in the lower trophic level is  transferred to the next trophic level.

In this example grass belongs to the first trophic level, producers.

Energy of grass=25000Kcal

Energy transferred to trophic level 2=10% of 25000=2500

10% of the energy in trophic level 2 is transferred to trophic level 3.

Hence energy at trophic level 3=10% of 2500=250Kcal

Energy transferred to trophic level 4=10% of energy in trophic level 3

                                                               =10% of 250=25Kcal

Energy to be stored in trophic level 4=25Kcal