Dexter sprinted for the first $600\textasciitilde m$ of a race in $160\textasciitilde s$ and jogged the remaining $\frac{2}{5}$ of the race in $240\textasciitilde s$. What was his average speed? 
选项为:A:$2.5\textasciitilde m/s$  B:$5\textasciitilde m/s$  C:$2\textasciitilde m/s$  D:$0.4\textasciitilde m/s$  请回答其中一个选项.