A chocolate company produces a box of 50 individually and identically wrapped chocolates. Supose this box of chocolates contains 10 dark chocolates and 50 milk chocolates (note bc indentically wrapped we don't know which flavour until eaten). If Sarah picks out 12 chocolates, what is the probability that she picks exactly 6 dark chocolates? Give the answer as a fraction but also as an exact expression with binomial coefficients