From December to February, there are 2 months that elapsed. Given that the number of units sold is increased by 4% every month, the units sold on February is calculated through the equation,
N = (10,000) x (1.04)^2
N = 10,816 staplers
Each unit is sold at a price of $16.90. Calculating for the total sales,
T = ($16.90)(10,816)
T = $182,790.4
Thus, the total amount of sales for the stapler is approximately $182,790.4.