Given,
Power consumed by the clothes iron, P=500 W
The time period during which the iron was operated, t=30 mins= 0.5 hours.
Cos of electricity per kWh, C=0.120 $
The energy consumed by the iron can be calculated as,

On substituting the values,

Therefore the cost of the electricity can be calculated as,

On substituting the known values,

Therefore the total cost of the electricity used by the iron is 0.03 $