From the information as given in the question, the transit time
for light from the sun would be
(6.1 x 10⁹ km) / (3.84 x 10³ km/sec) = 15,885 seconds (rounded).
(4.4 hours) .
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-- A better figure for Pluto's average distance from the sun is 5.874 x 10⁹ km.
-- " 384,000 km/sec " is about 28% too high for the speed of light.
A much better figure is 300,000 km/sec.
Using these numbers, the transit time is
(5.874 x 10⁹ km) / (3 x 10⁵ km/sec) = 19,580 seconds
(5.4 hours)