Let $$C_{1}$$ and $$C_{2}$$ be two biased coins such that the probabilities of getting head in a single toss are $$\frac{2}{3}$$ and $$\frac{1}{3}$$ , respectively. Suppose $$\alpha$$ is the number of heads that appear when $$C_{1}$$ is tossed twice, independently, and suppose $$\beta$$ is the number of heads that appear when $$C_{2}$$ is tossed twice, independently. Then the probability that the roots of the quadratic polynomial $$x^{2} − \alpha x + \beta$$ are real and equal, is