# Chapter 21: separate solutions

## Question 1

Compute default price of anarchy.

2/1.5=4/3.

## Question 2

Why exclude toll revenue from social travel time?

It is modeled as a transfer, not physical delay.

## Question 3

Compute transfer social optimum.

The optimal shortcut flow is z=capacity(constant_time-overhead)-demand=1(1-0)-0.5=0.5, which already lies within [0,0.5], so z=0.5. The total social time is (0.5+0.5)^2/(2(1))+1(0.5-0.5)+0(0.5)=0.5.