Answer
$$
0.90 \mathrm{\ m} / \mathrm{s}
$$
Work Step by Step
With $v=1540 \mathrm{m} / \mathrm{s}, \theta=20^{\circ},$
and $R=1+(5495 \mathrm{Hz}) /\left(5 \times 10^{6} \mathrm{Hz}\right)=1.0011,$
we use the expression above, to find speed of the blood:
$$
v_{\text {blood }}=\frac{(R-1) v}{(R+1) \cos \theta}=0.90 \mathrm{\ m} / \mathrm{s}
$$
