The sales function for a product $is$ given $byS(x)=93+29\mathrm{.}4x2-0\mathrm{.}7x3$

$,$ where $x$ represents thousands $of$ dollars spent $on$ advertising, $0x28$

$,$ and $Sisin$ thousands $of$ dollars.

Find the point $of$ diminishing returns. Enter the amount spent $on$ advertising $as$ well $as$ the sales $in$ dollars.