Additional Algo $19-1$ Early Start Time

The network diagram and task times for a project are shown below.

The process is as follows:A $1$ to A $2$ and A $3.$ A $2$ and A $3$ to A $4$ then A $5.$

Task Duration $($days$)$

A$1$

$7$

A$2$

$1$

A$3$

$4$

A$4$

$4$

A$5$

$7$

What is the early start time for activity A$5$

$?$