Electrical power = (voltage) times (current)
For this clock: Power = (120 volts) x (0.5 ampere) = 60 watts .
Note:
60 watts is the correct solution when you use the given information.
But 60 watts is a totally ridiculous power consumption for an electric
alarm clock. 2 to 5 watts would be reasonable ... maybe 15 to 25 watts
if it's part of a fancy clock+radio+telephone+night-light set.