a) How many hand-held color televisions can be sold at $ 400 per television?b) How many televisions will be sold when supply and demand are equal?c) Find the price at which supply and demand are equal.

a) Since we are interested in the number of TVs that can be sold at $400, we need to use the Demand model equation and set p=400; thus,
[tex]\begin{gathered} p=400 \\ \Rightarrow N=-7\cdot400+2820=20 \\ \Rightarrow N=20 \end{gathered}[/tex]The answer to part a) is 20 TVs per week.
b) Set N=N, then
[tex]\begin{gathered} N=N \\ \Rightarrow-7p+2820=2.4p \\ \Rightarrow9.4p=2820 \\ \Rightarrow p=\frac{2820}{9.4}=300 \\ \Rightarrow p=300 \end{gathered}[/tex]Therefore, using p=300 and solving for N,
[tex]\begin{gathered} \Rightarrow N=2.4\cdot300=720 \\ \Rightarrow N=720 \end{gathered}[/tex]The answer to part b) is 720 TVs per week.
c) In part b), we found that when supply and demand are equal, p=300. Thus, the answer to part c) is $300