Foundations of Relative Category Theory / 6. Other kinds of fibrations [0012] / 6.1. Cocartesian fibrations [0015] / 6.1.3. Example: The dual self-indexing [0019] / [001M] Exercise 6.1.3·b. Prove that $\overline{B}$ is a cocartesian fibration if and only if $B$ has pushouts. Construction 6.1.3·a [002Z] Exercise 6.1.3·c [001N]