It is given that the probability that one among two radioactive atoms will decay in an interval $x,x+dx$ and another one will decay in a time interval $y+dy$ is given by the following expression: $$Ne^{-y\alpha-x\beta-\gamma\sqrt{xy}}dydx$$ where $\alpha, \beta>0$, and $\gamma~\epsilon~R$.
How can I determine the expected value and standard deviation of decay time for both atoms in analytical form? Also, how do I numerically calculate the approx. probability that one of them decays prior to the other?