The nuclei of two radioactive isotopes of same substance `A^(236)` and `A^(234)` are present in the ratio of `4:1` in an ore obtained from some other planet. Their half lives are `30min` and `60min` respectively. Both isotopes are alpha emitters and the activity of the isotope with half-life `30min` is `10^(6)dps`. Calculate after how much time their activites will become identical. Also calculate the time required to bring the ratio of their atoms to `1:1`.