To find the percent efficiency using the provided formula:
\[ \text{Percent Efficiency} = \left(\frac{\text{Actual MA}}{\text{Ideal MA}}\right) \times 100 \]
Substituting the values:
- Actual MA = 10 J
- Ideal MA = 40 J
We have:
\[ \text{Percent Efficiency} = \left(\frac{10}{40}\right) \times 100 \]
Calculating that:
\[ \text{Percent Efficiency} = \left(0.25\right) \times 100 = 25% \]
Thus, the correct response is 25%.