$0\mathrm{.}05$ kg of a slightly soluble salt is mixed with $0\mathrm{.}1$ kg of water. the undissolved salt is removed by filtration. the filter cake weighed $0\mathrm{.}045$ kg as obtained and $0\mathrm{.}040$ kg after drying. what is the solubility of the salt in water expressed in kg salt$/100$ kg water?