A company collects 60% of its sales during the month of the sale, 30% one month after the sale, and 10% two months after the sale. The company expects sales of $10,000 in August, $20,000 in September, $30,000 in October, and $40,000 in November. How much money is expected to be collected in October?
a. $25,000
b. $15,000
c. $35,000
d. None of the above