(a) The distance between Earth and Voyager 2 was 35 AU, or
35 * 1.5 * 10^11 m = 5.25 * 10^12 m = 5.25 * 10^9 km.  So the
time taken by radio waves to arrive at Earth from Voyager 2 was

      distance    5.25 * 10^9 km
  t = -------- =  -------------- = 17500 sec = 4 hrs and 52 min.
      velocity     3 * 10^5 km/s

(b) At a speed of 40000 km/hr, Voyager 2 travelled a distance of

                     40000 km/hr
  d = speed * time = ----------- * 17500 sec = 1.94 * 10^5 km
                     3600 sec/hr

during the time a radio signal travelled to get from Voyager 2
to Earth - more than half the distance between Earth and the Moon.

(c) The flux of the transmitter on Earth's surface was

         Luminosity                  550 Watts
  F = ----------------- = ----------------------------- 
      4*pi*(distance)^2   4 * 3.14 * (5.25 * 10^12 m)^2

           = 1.59 * 10^(-24) Watts per square meter.