An urn contains 5 red and 5 black balls. A ball is drawn at random, its colour is noted and is returned to the urn. Moreover, 2 additional balls of the colour drawn are put in the urn and then a ball is drawn at random. What is the probability that the second ball is red?

Question

$\begin{array}{1 1}1/2 \\ 1/3 \\ 1/4 \\ 2/3 \end{array}$