At the end of 2019, the company had inventory (at cost) of $4,000 and inventory (at NRV) of $3,500. At the end of 2020, the cost of inventory went up to $4,500 and the NRV of inventory was $3,600. What is the amount for the adjustment that the company needs to make to the allowance account at the end of 2020? Assume 2019 was the company's first year of existence. $400 increase $900 decrease $100 increase $500 increase