Let's define how energy moves in a food web:
The primary producers will produce the most energy. From each successive level, it will be 10% of the energy transferred.
Let's apply this to the context of the problem:
We are given that a red squirrel has 4000 kJ of energy. We know that a red squirrel is a primary consumer and has a predator. That predator, in the secondary consumer level, is the fox. Since the fox is 1 level above the red squirrel, we can simply take 10% of the squirrel's energy:
4000 kJ(0.10) = 400 kJ
Therefore, our answer choice is the 1st answer choice.
