Problem 6.233

(a) What isotope is produced from the alpha-radioactive $\mathrm{Ra}^{226}$ as a result of five alpha-d isintegrations and four $\beta$ - -disintegrations? (b) How many alpha- and $\beta$ -decays does $U^{238}$ experience before turning finally into the stable $\mathrm{Pb}^{206}$ isotope?