Before revision:  For a Cobb-Douglas production function, if the diffusion's coefficients are constant, we are able to show that the free boundary is a continuous function of the time so to remove Assumption- Cfb in Chiarolla and Haussmann (2009) .
After revision:  For a Cobb-Douglas production function, if the diffusion's coefficients are constant, we are able to show that the free boundary Cfb in Chiarolla and Haussmann (2009) .