please it is very important: In a nuclear reactor, waste material with a concentration of $0\mathrm{.}3510^-3$ kg$/$L is obtained at a rate of $40$L per minute. The solution will be allowed to sit for a while to reduce the concentration of this waste material to a safe limit$.$ If the concentration drops to $0\mathrm{.}03510^-3$ kg$/$L$,$ the danger is eliminated. The waste material, which is a radioactive isotope, decays proportionally to its own concentration. a$)$ What should be the volume of a sufficiently large tank to reduce the concentration of this waste material to a safe level by letting it sit in the tank? $($k $=0\mathrm{.}0693$ min$^-1)$ b$)$ When a second flow is sent to the same tank $(40$L$/$min$)$: i$.)$ If the flow is water ii$.)$ If the flow contains $0\mathrm{.}5*10^-3$ kg$/$L waste material what will be the volume?