40 men can complete a piece of work in 15 days. 20 more men joined them after 5 days they start doing work. How many days will be required by them to finish the remaining work ?

• A. ${\text{7}}\frac{2}{3}{\text{ days}}$$
• B. ${\text{6}}\frac{1}{5}{\text{ days}}$$
• C. ${\text{8}}\frac{1}{4}{\text{ days}}$$
• D. ${\text{6}}\frac{2}{3}{\text{ days}}$$