Using proportions, it is found that his total electricity cost for the fans during one year is given by:
b. $3.84
A proportion is a fraction of a total amount.
In this problem, for 3 months, he uses 4 portable fans, and each fan is on for about 96 hours per month, hence the total number of hours he uses it is:
4 x 96 = 384 hours.
The cost is one one cent per hour, hence:
$0.01 x 384 = $3.84.
Which means that the total cost is of $3.84, and option b is correct.
More can be learned about proportions at https://brainly.com/question/24372153