A bag contains 6 white and 4 black ball. Two balls are drawn at random. Then the probability of getting balls of the same colour is ____.

$\frac{8}{15}$ $\frac{6}{15}$ $\frac{6}{13}$ $\frac{7}{15}$

$\frac{7}{15}$

The correct answer is Option (4) → $\frac{7}{15}$