The value of the investment at the time t+∆t is then given by S(t+Δt)=S(t)+(rΔt)S(t)+kΔt, where at the end of the time interval ∆t, rΔtS(t) is the...The value of the investment at the time t+∆t is then given by \boldsymbol{\label{eq:1}S(t+\Delta t)=S(t)+(r\Delta t)S(t)+k\Delta t,} where at the end of the time interval ∆t, rΔtS(t) is the amount of interest credited and k∆t is the amount of money deposited (k>0) or withdrawn (k<0).
