ANSWER:
a) 1.91 cm/s
b) 0.039 cm/s
Explanation:
a)
Here, since we need the velocity in cm/s, we assume that a small volume of blood passes through the section of the arteriole in a given time.
So, we have to divide the blood flow by the area of the arteriole section, therefore:

d = 0.08 mm = 0.008 cm
Replacing:

We calculate the speed by dividing the rate by the previous calculated area, like this:

b)
First we find the area of the section of the capillaries:

Now we have to remember that the flow is dividid in equal parts, so the volume by seconds is:

So the speed in this case is:

This latter speed is less than in the main arteriole.