$17.$ A project is $2\mathrm{.}5$ miles wide to be flown at $2500$ ft$.$ flying height with a $9$x$9$ in$.$ format $6$ in$.$ focal length camera at $30\%$ sidelap. If the first and last flight line cannot be flown inside the project area, the approximate number of flight lines is closest to

$($a$)3$

$($b$)7$

$($c$)11$

$($d$)15$