Answer:
0.625 (62.5 %)
Step-by-step explanation:
The production efficiency is equal to the rate between the energy converted into useful energy and the energy in input:

where in this case:
- the useful energy is 750 J (the energy used in cellular respiration)
- the energy in input is 1200 J (the energy taken by eating the seeds)
Substituting,

Which means an approximate efficiency of 62.5 %.