A product sells by word of mouth. The company that produces the product has noticed that revenue from sales is given by R(t) = 211Q, where x is the number of units produced and sold. If the revenue keeps changing at a rate of $300 per month, how fast is the rate of sales changing when 300 units have been made and sold? (Round to the nearest dollar per month.) C) D. $2,598/month $171month $5, 196/month $20,785/month