$\mathrm{compartment}\mathrm{beta\_x}\mathrm{psi}$ $\mathrm{compartment}\mathrm{alpha\_x}x$ $\frac{\mathrm{compartment}\mathrm{alpha\_k}yx}{x+k}$ $\mathrm{compartment}\mathrm{beta\_y}x\mathrm{psi}$ $\mathrm{compartment}\mathrm{alpha\_0}\mathrm{y0}$ $\mathrm{compartment}\mathrm{alpha\_y}y$