All things being equal; demand decreases, as price increases.
The quantity supplied when price is $4 is 28
From table 4.4 (see attachment).
When price = $4, we have the following supplies:
So, the total supply at $4 is:
[tex]Total = 4 + 6 + 8 + 10[/tex]
[tex]Total = 28[/tex]
Hence, the quantity supplied when price is $4 is 28
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