**Answer :**

According to the question, the radius of the vein is

**r = 2 × 10 ^{-3} m**

And the diameter of the vein is

**d = 2 × 1 × 10 ^{-3} m = 2 × 10^{-3} m**

The viscosity of blood is given by

**η ****= 2.08 x 10 ^{-3} m
**The density of blood is

**ρ = 1.06 × 10 ^{3} kg/m^{3}**

**(a) It is known that N _{R} = 2000, i.e., Reynolds’ number for laminar flow**

Therefore, expression for the greatest average velocity of blood is

(b) The flow rate is given by

**R = Vavg π r ^{2}**

**R = 0.983 x 3.14 x ( 10 ^{-3})^{2}**

**R = 1.235 x 10 ^{-6} m^{3}/s**