Graph Algorithms · Challenge problem

A delivery network has vertices $s,a,b,c,t$ and roads $sa{:}5, sb{:}9, ab{:}3, ac{:}8, bc{:}2, bt{:}10, ct{:}4$, where each weight is that road's risk level. A route's overall risk is governed by its SINGLE riskiest road. Over all routes from $s$ to $t$, what is the smallest possible value of that route's riskiest road?