plz solve 2, 3, and 4

1. Which particle(s) are emitted in the radioactive decay process shown below? 92238U90234Th 2. Determine the radioactive decay constant for radon. The half-life is 3.825d. 3. A radioactive element has a half-life of 30 years. If the initial amount of the element is 1.0mg, after 90 years, the amount remaining is most nearly (mg) : 4. The following dose-response curve was developed for a carcinogenic compound. The potency factor is most nearly [in units of (mg/kg-day )1 ]