Problem 6.231

A radionuclide $A_{1}$ goes through the transformation chain $A_{1} \rightarrow A_{2} \rightarrow A_{3}$ (stable) with respective decay constants $\lambda_{1}$ and $\lambda_{2} .$ Assuming that at the initial moment the preparation contained only the radionuclide $A_{1}$ equal in quantity to $N_{10}$ nuclei, find the equation describing accumulation of the stable isotope $A_{3}$.