Answer
We can rank the shuttle craft according to the frequencies they detect:
$(1) \gt (4) \gt (2) \gt (3)$
Work Step by Step
We can write an expression for the received frequency when a receiver is moving away from the source with a speed $v$:
$f = f_0~\sqrt{\frac{1-v/c}{1+v/c}}$
We can see that $f \lt f_0$ and the received frequency $f$ decreases as $v$ increases.
We can list the speed at which each shuttle craft moves away from each respective cruiser:
(1) $v_s = 0.40c$
(2) $v_s = 0.70c$
(3) $v_s = 0.90c$
(4) $v_s = 0.60c$
We can rank the shuttle craft according to the frequencies they detect:
$(1) \gt (4) \gt (2) \gt (3)$
