is this answer correct: $2$a$.$

Paths:

$1-2-5-7=4+7+5=16$ weeks

$1-3-5-7=6+3+5=14$ weeks

$1-3-6-7=6+5+2=13$ weeks

$1-4-3-5-7=5+3+5=13$ weeks

$1-4-3-6-7=5+5+2=12$ weeks

$1-4-6-7=5+4+2=11$ weeks

Critical path $=$longest path $=1-2-5-7($A$-$D$-$H$)$

Length $=16$ weeks

$2$b$.$

Activity A is critical, therefore, slack $=0$

$2$c$.$

We shall crash $5-7($H$)$ by $2$ weeks, then $1-2($A$)$ by $1$ week