A regression model between sales $($y in $$1000$s$),$ unit price $($x$1$ in dollars$)$ and television advertisement $($x$2$ in dollars$)$ resulted in the following function: y$\_$hat $=73$x$1+5$x$2$ For this model, SSR $=3500,$ SSE $=1500,$ and the sample size is $18.$ Refer to Exhibit $2.$ The coefficient of determination for this problem is $\_\_\_\_\_.0\mathrm{.}360\mathrm{.}490\mathrm{.}700\mathrm{.}87$