Question is incomplete. Complete question has been attached.
Answer:
A simple aquatic food chain with the top predator as Baleen whale could look like:
Diatoms ⇒ Krill ⇒ Baleen whale
Only 10% of energy at one level is passed on to the next level. Hence, only 10% of biomass at one level is converted to biomass in the next level.
If a Baleen whale wants to gain 7.5 kgs at third trophic level, it means there should be 75 kg of Krill present in second trophic level. Similarly, there should be 750 kg of diatoms present in the first trophic level. Hence, 750 kgs of diatoms are required for a Baleen whale to gain 7.5 kgs.