Graph Algorithms · Superchallenge problem

A weighted graph has vertices $s,a,b,c,d,t$ and edges $sa{:}2, sb{:}7, ab{:}3, ac{:}5, bc{:}1, bd{:}8, cd{:}2, ct{:}9, dt{:}3$. What is the length of the SECOND shortest route from $s$ to $t$ (the shortest route that is NOT the overall shortest)?