From the data collected on a freeway section, the following equation was extracted

for the relationship between the speed $(v$ in $k\frac{m}{h}r)$ and density $(k$ in veh$/km)$:

$v=200-0\mathrm{.}4k$

a$)$ What is the free$-$flow speed on the freeway? $(0\mathrm{.}5$ mark$)$

b$)$ What is the critical density and the speed and traffic flow achieved at critical

density? $(1\mathrm{.}5$ marks$)$

c$)$ What is the jam density achieved at this freeway section? $(0\mathrm{.}5$ mark$)$