In a process, the total energy input $E_{\text{in}}$ is divided so that some is passed on as useful energy output $U$, while the remainder is passed on as wasted energy $W$. What is the efficiency of the process?
- A$\frac{U}{E_{\text{in}}} \times 100\%$
- B$\frac{W}{E_{\text{in}}} \times 100\%$
- C$\frac{U}{W} \times 100\%$
- D$\frac{U + W}{E_{\text{in}}} \times 100\%$