HI! I'm getting stuck in forming the Private and Social Marginal Cost Equations for Lane 1 and Lane 2

The Qubec government is planning to build a toll highway connecting new

suburban growth areas with Montral. It must decide whether to build a road

with one or two lanes.

Suppose that the first lane begins to get congested at a volume of 10,000

vehicles per day. Each additional 1,000 vehicles reduce the speed of all cars on

the lane by 1 km per hour. If the road is twice as wide, congestion kicks in at

20,000 vehicles but now declines by 1 km per hour for each 2,000 additional

vehicles.

The free-flow speed is 100 km/h.

Suppose that the only variable cost on this road is the cost of drivers' time, which

they value at $10/hour and the length of the road is 50 kilometers. All drivers

travel on this full segment. Find the equation of the PMC and SMC for 1-lane and 2-lane roads