A radioactive sample consist of two distinct spices having equal number of atoms initially. The mean life one spices is τ and that of other 5τ. The decay products in both cases are stable. The following figure shows graphs P, Q, R, S the plot of the total number of radioactive nuclei as a function of time. Which of the graphs P, Q, R and S represent the best form of the plot?
(1) P
(2) Q
(3) R
(4) S