1) To calculate it the length, let's use the distance formula for EF
where we pick the coordinate of E(-8,3) and F(8,3) and plug it into this formula derived from the Pythagorean Theorem
So,
[tex]d_{EF}=\sqrt{(3-3)^2+(8-3)^2}=5[/tex]2) So the length of EF is 5 units
