[ ] Write the coupled differential equations $dN_i/dt = -\lambda_i N_i + \lambda_{i-1} N_{i-1}$ for all members of the chain - [ ] Solve numerically using the toolkit's `decay_chains.py` module (or equivalent ODE solver) - [ ] Plot the number of atoms $N_i(t)$ and activity $A_i(t) = \lambda_i N_i(t)