The answer will depend on several things for which no information is available:
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None!!!
Reasons,
#1 you have not described the units of measure in the figures.
#2 In multiplying these figures together , the result would be 'units^(3)'. NOT linear inches.
39.25 inches
63. The inch is a linear measurement, so the adjective is unnecessary.
12 INCHES
80 inches is 6.66 feet.
12 inches is equivalent to 1 foot.