Final answer:
Net primary production is the energy that remains in the primary producers after accounting for respiration and heat loss. The formula for calculating it is Photosynthesis - Respiration.
Step-by-step explanation:
Net primary production is the energy that remains in the primary producers after accounting for respiration and heat loss. It can be calculated by subtracting the rate of respiration from the rate of photosynthesis. Therefore, the correct answer is Photosynthesis - Respiration.