A video game includes an asteroid that is programmed to move in a straight line across a $17-$inch monitor according to the equation $x=6\mathrm{.}5t-2\mathrm{.}3t^3,$ where x is in inches and t is in seconds. At some point during the trip across the screen, the asteroid is at rest. What is the asteroid's acceleration at this point?

Select one:

$$ a$.6\mathrm{.}5i\frac{n}{s^2}$

b$.-11i\frac{n}{s^2}$

c$.0\mathrm{.}40i\frac{n}{s^2}$

d$.-13i\frac{n}{s^2}$