A project starts with activity $A$ and ends with activity $F$. The precedence relation and durations of the activities are as per the following table:
$$\begin{array}{|l|l|l|} \hline \text{Activity} & \text{Immediate predecessor} & \text{Duration (days)} \\ \hline A& – & 4\\ \hline B & A & 3 \\ \hline C & A & 7 \\ \hline D & B & 14 \\ \hline E & C & 4 \\ \hline F & D, E & 9 \\ \hline \end{array}$$
The minimum project completion time (in days) is _________.