Microsoft has accounts receivable totaling $500,000. An analysis of these receivables reveals that $200,000 are less than 30 days old, $150,000 are between 31 and 60 days old, $100,000 are between 61 and 90 days old, and $50,000 are over 90 days old. Calculate the total allowance for doubtful accounts using the following percentages for each age category: 2% for less than 30 days, 5% for 31-60 days, 10% for 61-90 days, and 20% for over 90 days.