we know that
The school paid a unit price ($) per book of
[tex] \frac{1,137.50}{350} =3.25 [/tex]
$[tex] 3.25 [/tex] per book.
In order to make a profit of $1,500, the agenda books need to be
sold for a minimum of
[tex] 3.25+\frac{1500}{350} =3.25+4.29\\ =7.54 [/tex]
$[tex] 7.54 [/tex] per book.
Check
$[tex] 7.54*350 [/tex] brings revenue of
$[tex] 2,639 [/tex],
and [tex] (2,639-1,137.50) [/tex] gives profit of
$[tex] 1,501.50 [/tex]
therefore
the answer is
$[tex] 7.54 [/tex] per book.