The trees are the primary producers that produces the food on which the consumers are dependent. This forms the base of the ecological pyramid for both energy as well as biomass.
In any biological condition, it can be observed that during its ecological succession from one trophic level to the next, almost 90% of its total energy is lost, and only 10% of its energy is transferred to the successive trophic level.
Similarly, biomass is also comparatively higher in producers like plants and trees than in any other trophic levels.
You just put the numbers in order from least to greatest and its the middle one. if there's an even amount of numbers, you add the middle two and divide by 2