For the period 2013-2020 if x is the numerical value of percentage increase/decrease in the average value of the products list price in the fist four years as compared to the average value of the products list price in the last four years and y is the numerical value of percentage increase/decrease in the average value of the products net price in the 15 four years as compared to the average value of the products net price in the last four years, Calculate the value of $$\sqrt{3x+19y}$$.

Average list price of the first four years: $$\frac{3+6+8+7}{4}=6$$
Average list price of the last four years: $$\frac{5+9+8+10}{4}=8$$
Increase = 2
percentage increase : $$\frac{2}{6}\times\ 100=\frac{100}{3}$$  {x}

Average net price of the first four years: $$\frac{2000+5000+7000+5000}{4}=\frac{19000}{4}$$
Average net price of the last four years: $$\frac{3000+6000+5000+8000}{4}=\frac{22000}{4}$$
Increase = $$\frac{3000}{4}$$
Percentage increase: $$\frac{3000}{4}\times\ \frac{4}{19000}\times\ 100=\frac{300}{19}$$  {y}

Putting these values in the given term we get:
$$\sqrt{\left(\ 3\times\ \frac{100}{3}\right)+\left(19\times\ \frac{300}{19}\right)}$$
$$\sqrt{\ 400}=20$$

Therefore, Option A is the correct answer.