Simplify the given expression completely.



(2r6s10)(5r7s9)5r5s8=\displaystyle \frac{{{\left(-{2}{r}^{{6}}{s}^{{10}}\right)}{\left(-{5}{r}^{{7}}{s}^{{9}}\right)}}}{{{5}{r}^{{5}}{s}^{{8}}}}=