$\begin{array}{1 1}(a)\;k_1=\large\frac{1}{t}\normalsize ln\large\frac{P_i}{P_i-P}\\(a)\;k_1=\large\frac{1}{t}\normalsize ln\large\frac{2P_i}{2P_i-P}\\(c)\;k_1=\large\frac{1}{t}\normalsize ln\large\frac{2P_i}{3P_i-P}\\(d)\;k_1=\large\frac{1}{t}\normalsize ln\large\frac{P_i}{3P_i-P}\end{array}$