Fill in the information in the following proof for this argument

$(WG)$

$(AP)$

$(WvvA)$

$|(PvvG)|$

$1P,$ from $4$ by NOR

$1A$ from

$IW$ from

I G from $1,7$ by IF THEN

$|G,|$ from $4$ by NOR

$10.|$G from $9$ by NN

:$.(PvvG)$ from $4-9$ by $RA$

What is the missing justification for line $4?$

line $3$

line $1$

assumption for RA

line $2$