Average Speed Questions

A car covers $20\text{km}$ in the first quarter of an hour, $25\text{km}$ in the second quarter of that hour and $15\text{km}$ in the third quarter. The average speed of the car (in $\text{km/h}$) over the entire journey is:

A bus covers the first $50\text{km}$ of its journey in $40$ minutes and covers the remaining $75\text{km}$ in $40$ minutes. What is the average speed (in $\text{km/h}$) of the bus?