Let C1 and C2 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 $\mathrm{C}_1$ is tossed twice, independently, and suppose $\beta$ is the number of heads that appear when $\mathrm{C}_2$ is tossed twice, independently, Then probability that the roots of the quadratic polynomial $x^2-\alpha x+\beta$ are real and equal, is