Answer:
65.63 cm or 65 5/8 cm
Step-by-step explanation:
volume of a rectangular prism = whl
w= 7 1/2
h = 2 1/2
l = 3 1/2
w x h x l
This is how it would look like, hope that this is not too late to help you yet!
Have a great day!
The midpoint formula for a segment is:

apply to points R and P

using the definition of slope find the slope of the segment

apply to points R and P

to lines are parallel when the slopes are the same

two lines are perpendicular when the product of the slopes is equal to -1