Suppose that $z$ is a linear function of $x$ and $y$ with slope -5 in the $x$ direction and slope 5 in the $y$ direction.

(a) A change of $0.2$ in $x$ and $0.5$ in $y$ produces what change in $z$?
change in $z =$

(b) If $z=6$ when $x=3$ and $y=2$, what is the value of $z$ when $x=2.7$ and $y=1.9$?
$z =$