Use for the following $7$ questions:

Vesper Auto Wash is reviewing its sales for the last $9$ months. Executives at Vesper are in disagreement over the driving force behind sales of their basic carwash package. Some argue it is the price of a carwash, while others argue it is the number of ads on the radio. The data for the monthly sales of basic carwashes, the corresponding price, and the number of monthly radio ads are presented below.

Sales

Price

Ads

$7,006$

$10\mathrm{.}7$

$61$

$7,234$

$10\mathrm{.}46$

$73$

$7,692$

$10\mathrm{.}21$

$84$

$7,486$

$10\mathrm{.}51$

$78$

$7,526$

$10\mathrm{.}26$

$82$

$8,012$

$10\mathrm{.}12$

$96$

$8,121$

$10\mathrm{.}01$

$104$

$7,924$

$10\mathrm{.}11$

$100$

$8,131$

$9\mathrm{.}99$

$109$

What would be the multiple regression equation for examining the relationship among sales, price, and the number of radio waves?