Directed Graphs and Network Flows · Medium problem

A flow network has source $s$, sink $t$, and vertices $a,b,c$, with capacities $c(s,a)=8$, $c(s,b)=5$, $c(a,b)=1$, $c(a,c)=6$, $c(b,c)=4$, $c(b,t)=2$, $c(c,t)=9$. A flow sends $f(s,a)=6$, $f(s,b)=5$, $f(a,b)=1$, $f(b,t)=2$, with $f(a,c)$ and $f(b,c)$ left to satisfy conservation at $a$ and $b$, and $f(c,t)$ fixed to balance $c$. What is the value of this flow?