Answer: $228 is spent by her overall.
Explanation:
Since we have given that
Number of dimmer switches = 12
Cost of dimmer = $25
Total cost will be

According to question, he will receive $6 credit for each one she returned .
Number of switches she returned = 12
Total amount she will be credited is given by

Total amount she spend overall is given by

Hence, $228 is spent by her overall.