Suppose that $z$ is a linear function of $x$ and $y$ with slope $2$ in the $x$-direction and slope $4$ in the $y$-direction.

(a) A change of $-0.8$ in the $x$-direction and $0.1$ in the $y$-direction produces what change in $z$?
change in $z$ is

(b) If $z = 5$ when $x = 5$ and $y = 6$, what is the value of $z$ when $x = 4.4$ and $y = 6.6$?
$z =$