In a horizontal capillary tube, the rate of capillary flow depends on the surface tension force as well as the viscous force. Lueas and washburn showed that the length (x) of liquid penetration in a horizontal capillary depends on a factor (k) apart from time (t). The factor is given by $\mathrm{k}={\left[\frac{\mathrm{rTcos}\mathrm{\theta }}{2\mathrm{\eta }}\right]}^{\frac{1}{2}};$ where r, T, $\mathrm{\theta }$ and $\mathrm{\eta }$ are radius of the capillary tube, surface tension, contact angle and coefficient of viscosity respectively. If the length of liquid in the capillary grows from zero to x₀ in time t₀, how much time will be needed for the length to increases from x₀ to 4x₀.