Question 1045993
$6 each ===> 3,800 curtains per month
$11 each ===> 3,600 curtains per month.


===> slope of the demand line is {{{(3800 - 3600)/(6-11) = 200/(-5) = -40}}}.

===> demand function is q = -40p + c  for some constant c.

Let 3,800 = -40*6 + c.

===> c = 4,040.

Therefore the linear demand function is  q = -40p + 4,040.