where α is the instantaneous expected rate of return on the firm per unit time, C is the total dollar payouts by the firm per unit time to either its shareholders or liabilities-holders (e.g., dividends or interest payments) if positive, and it is the net dollars received by the firm from new financing if negative;
σ
2
σ2 is the instantaneous variance of the return on the firm per unit time; dz is a standard Gauss-Wiener process.