Answer
(a) $9.46\times 10^{12}Km$
(b) $1.00~light \space year/year$
(c) $0.98~4ft/ns$
Work Step by Step
(a) We can express 1 light year(ly) in Km as follows:
$1~light \space year=(3\times 10^8m/s)(365days)(\frac{86400s}{day})$
$1~light \space year=9.46\times 10^{15}m=9.46\times 10^{12}Km$
(b) The speed of light in units of ly per year can be expressed as
$1~light \space year=9.46\times 10^{15}m$
$\implies 1m=\frac{1}{9.46\times 10^{15}}light\space year$
We know that the speed of light is $c=3\times 10^8m/s$
$\implies c=\frac{(3\times 10^8)(\frac{1}{9.46\times 10^{15}})}{365\times 86400}$
$c=1.00~light \space year/year$
(c) The speed of light in feet per nanosecond can be expressed as
$c=(3\times 10^8m/s)(\frac{1s}{10^9ns})(\frac{1ft}{0.3048m})$
$c=0.984~ft/ns$
