$($a$)$ Calculate the bit$-$rate that would be required to address all of the $6$ million subpixels $$of an HD TV screen at a $($refresh$)$ rate of $60$ per second. $($b$)$ Compare to the present$-$day digital fixed rate of $,$and explain the difference. $($c$)$ On average, what $\%$ of pixels get refreshed for each frame $($refreshed at $60$ Hz$)?($d$)$ If it were necessary to address every pixel for each frame, how many full scans of the screen could be done per second at $?$