Additional Algo $19-4$ Late Finish Time

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

Duration $($days$)$

Task

$A_1$

$A_2$

$A_3$

$A_4$

$A_5$

$6$

$6$

$3$

$1$

$4$

What is the late finish time for activity $A_1?$

Late finish time

days