Problem $3$: Average Flow Speed

It is possible to define an $$average$$ flow velocity, $<$ v $>,$ for blood flow rate, Q$,$ through a blood vessel of cross$-$sectional area A via Q $=<$ v $>$ A$.$ The average speed of blood in the aorta is $0\mathrm{.}3$ m s$1$ and the radius of the aorta is $1$ cm$.$ There are about $2109$ capillaries with an average radius of $6$ m$.$ What is the average speed of blood flow in a capillary