Let $g(x,y)=cos(x4y).$

$($a$)$ Evaluate $g(4,-1).$

$g(4,-1)=$

$($b$)$ Find the domain of $g.$

$-4x4,-1y1$

$-1x4y1$

$-1x1,-\frac{1}{4}y\frac{1}{4}$

$-\frac{}{2}x4y\frac{}{2}$

$R^2$

$($c$)$ Find the range of $g.($Enter your answer using interval notation.$)$