\[\boxed{\text{191\ (191).\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[\textbf{б)}\ t = 1\ ч:\]
\[v = 80\ \frac{км}{ч}\text{.\ }\]
\[t = 4\ ч:\]
\[v = 22,5\ \frac{км}{ч}\text{\ .}\]
\[t = 8\ ч:\]
\[v = 11\ \frac{км}{ч}\text{.\ }\]
\[t = 16\ ч:\]
\[v = 4\ \frac{км}{ч}.\]
\[\textbf{в)}\ s_{\text{AB}} = 50 \cdot 2 = 100\ км.\]