A Riemann sum approximates the area of a certain region. Usually it's used in calculus, where you use the Riemann sum to approximate the area a curve instead of using an integral to find the exact value, since that tends to take a lot more time and effort.
The answer to this is 15 because you would multiply 5*3 to get you answer or you could do 5+5+5 either way it equals 15
D is true hope this helps
