\[\frac{8m + 8n}{a^{5}} \cdot \frac{5a^{10}}{m^{2} - n^{2}} =\]
\[= \frac{8(m + n) \cdot 5a^{10}}{a^{5}(m - n)(m + n)} = \frac{40a^{5}}{m - n}\]