Troista Mobile Accessories sells mobile apps on their Web site. If a customer spends on average, $12 per visit and visits the Web site 20 times each year, what is the average nondiscounted gross profit during a customer's lifetime? Given that Troista makes a margin of 60 percent on the average bill, with 25 percent of customers not returning each year.
A) $30
B) $360
C) $576