A national fast food company has just analyzed the effect of the latest sales promotion.

It has determined that the sales decay for its milkshakes is given by $S=360,000e^{-0\mathrm{.}8x},$ where $S$ is the

weekly sales and $x$ is the number of weeks that have passes since the end of the sales promotion.

a$)$ Determine the sales $3$ weeks after the end of the promotion:

Round answer to $2$ decimal places.

Sales $=$$

b$)$ If no new campaign is started, how many weeks after the end of the promotion will sales drop below

$30,000?$

Round answer to $1$ decimal place.

Num. weeks $=$