$3\mathrm{.}15$ It is required to determine the water content of a wet sample of silty sand weighing $400$ g $.$

This mass of soil was placed in a pycnometer and water filled to the top of the conical cup

and weighed $(M_3).$ Its mass was found to be $2350$ g $.$ The pycnometer was next filled with

clean water and weighed and its mass was found to be $2200g(M_4).$ Assuming $G_s=2\mathrm{.}67,$

determine the water content of the soil sample.