Consider the cities ${L, M, N, O, P, Q}$. The costs of the possible roads between cities are given below:

$c(L,M)=8$
$c(L,N)=9$
$c(L,P)=7$
$c(M,O)=5$
$c(M,Q)=4$
$c(N,P)=6$

What is the minimum cost to build a road system that connects all the cities?