Yes, they cross each other and make an angle of 90° or right angle.
the slope of the perpendicular line to the line through the two points is 0
Another way to solve this is to use the Midpoint Formula. The midpoint of a segment joining points

and

is

So the midpoint of your segment is

Perhaps it helps to see that the x-coordinate of the midpoint is just the average of the x-coordinates of the points. Ditto for the y-coordinate of the midpoint; just average the y's.
V=448 in^3
l=8 in
w=12
h=?
V=l•w•h/3
448=8•12•h/3 multiply both sides by 3
3•448=96•h
1344=96•h
h=1344/96
h=14 in
V=l•w•h/3
h=4in
l=3in
w=2.5 in
V=?
V=4•3•2.5/3
V=30/3
V=10 in^3