Amar Jeet Singh can complete a piece of work in 5 days. With the help of his son he can complete it in 3 days. In how many days can the son independently complete the work?
6 \( \frac{1}{2} \)
7 \( \frac{1}{2} \)
5 \( \frac{1}{2} \)
4 \( \frac{1}{2} \)
Find the value of 0.4 + \( \frac{404}{1000} \)