A study was conducted in which water was pumped through cylindrical pipes made of a sparingly soluble solid. For a given pipe and certain flow conditions, the mass transfer coefficient k${_c}$ has been calculated as 1 mm/s using the correlation

Sh = 0.025 Re$^{0.6}$ Sc$^{0.33}$

If the velocity of the fluid and the diameter of the pipe are both doubled, what is the new value of k${_c}$ in mm/s, up to 2 digits after the decimal point? $\_\_\_\_\_\_\_$