There are two radio-active nuclei `A` and `B`. `A` in an alfa-emitter while `B` is a beta-emitter, Their disintegration constant are in the ratio of `1:4`. The ratio of number of nuclei of `A` and `B` at any time `'t'` such that probabilities of getting number of alpha and beta particles are same at the instant is `y:1`. Then `y`______is