A function $z(x, y)$ of $x$ and $y$ is given by the formula
$z = 2r^2 \cos(5\theta)$, where $r$ and $\theta$ are the usual polar
coordinates. Starting at the point corresponding to $r = 3$ and
$\theta = \pi/6$, the corresponding $x$ and $y$ values are changed
by adding .1 to $x$ and adding .15 to $y$. If $A$ is the
estimated change in $z$ obtained from the linear approximation
applied to $z(x, y)$, then the value of $\sin(3A)$ is
