Answer :
We will have the following:
a) We determine the average speed for the trip as follows:
[tex]\begin{gathered} s_a=\frac{((85km/h)(0.25h)+(80km/h)(19/60h)+(45km/h)(0.5h))/(109/60h)}{3} \\ \\ \Rightarrow s_a=\frac{4145}{327}km/h\Rightarrow s_a\approx12.68km/h \end{gathered}[/tex]So, the average speed of the whole travel is approximatey 12.68 km/h.
b) We determine the distance between the intitial and final cities as follows:
[tex]\begin{gathered} d=(85km/h)(0.25h)+(80km/h)(19/60h)+(45km/h)(0.5h)\Rightarrow d=\frac{829}{12}km \\ \\ \Rightarrow d\approx69.08km \end{gathered}[/tex]So, the distance is approximatey 69.08 km between the cities.