1. The problem gives the function $$E(t)=11.5\sin\left(\dfrac{2\pi}{365}(t-18) \right)+25$$ which models daily electrical output in kilowatt hours for day $$t$$ of the year. 2. We are asked about the meaning of the solution set to the equation $$y=11.5\sin\left(\dfrac{\pi}{2}\right)+25$$. 3. First, evaluate the right side: $$\sin\left(\dfrac{\pi}{2}\right)=1$$ So, $$y=11.5 \times 1 + 25 = 11.5 + 25 = 36.5$$ 4. This value $$y=36.5$$ kWh represents the electrical output at the peak sine value (since sine reaches maximum 1 at $$\pi/2$$). 5. Thus, $$y=36.5$$ kWh is the maximum daily electrical output the solar panels can produce. 6. The question asks about the "solution set" to the equation involving this maximum output value in the model's sine argument: $$11.5\sin\left(\dfrac{2\pi}{365}(t-18) \right)+25 = 36.5$$ Solving this equation gives all $$t$$ values (days) when output equals maximum 36.5 kWh. 7. Therefore, the solution set corresponds to the days of the year when solar panel output is at its maximum. Final answer: Choice D - The set of all days of the year on which the solar panels output their maximum number of kilowatt hours