Answer
$JH\text{ exists}$
Work Step by Step
The $row\times column$ dimension of matrix $J$ is $1\times2,$ while matrix $H$ is $2\times1$. Since the column dimension of $J$ (equal to $2$) is equal to the row dimension of matrix $H$ (equal to $2$), then the matrix product $
JH\text{ exists}
.$