Graph Algorithms · Medium problem

A project has tasks $p,q,r,s,t,u,v$ with durations (days) and prerequisites $p \to q$ ($5$), $p \to r$ ($3$), $q \to s$ ($2$), $r \to s$ ($4$), $r \to t$ ($6$), $s \to u$ ($3$), $t \to u$ ($2$), $u \to v$ ($1$). Each number is how many days that task itself takes. What is the earliest day task $u$ can be completed, counting from day $0$?