A product sells by word of mouth. The company that produces the product has noticed that revenue from sales is given by 3 square root of x where x is...

A product sells by word of mouth. The company that produces the product has noticed that revenue from sales is given by 3 square root of x where x is the number of units produced and sold. If the revenue keeps changing at a rate of per month, how fast is the rate of sales changing when 1400 units have been made and sold?