Answer:50 Oak trees, 30 squirrel, 15 owls
Explanation: In an ecosystem energy flows through different trophic levels. It goes from producers such as trees then primary consumers or herbivores and then secondary consumers or predators.
In every level, some energy is lost due to the biological processes of each group. So, in order to keep a balance, is important to have more energy available at lower levels, that is why there should be more individuals of Oak trees, then squirrel and finally owls