I will explain my process using the image with my work and knowledge. So, the question is asking us how much energy is transferred from the producers to the primary consumers.
Step 1: I illustrated the question to get a visual representation by drawing a energy pyramid.
Step 2: Consider the 10% rule. It states that only 10% of energy is actually passed down from each tropic level. The 90% is gone as heat, used from metabolism, and etc by the organism. So, the producers passes down 10% of its energy to the primary consumers who are just one level above. The higher the organism in the pyramid, the less energy it obtains.
Step 3: Take the energy the producers have and multiply it by the 10%. Of course we cannot multiply by percentage so convert it into a decimal (0.10) and we get 15000 kJ
Step 4: 15000kJ of energy is transferred to the primary consumers