Answer
$-4 \overrightarrow{ j} $
Work Step by Step
We can see that the notation $\lt a, b \gt $ is same as that of $a \overrightarrow{i} +b \overrightarrow{ j}$
We have: $ a=0 $ and $b = -4$
Thus, our answer becomes:
$a \overrightarrow{i} +b \overrightarrow{ j} =0 \overrightarrow{i} +(-4) \overrightarrow{ j}= -4 \overrightarrow{ j} $
