A student saturates $350\ \text{g}$ of water with a salt at $60\ ^\circ\text{C}$, where $90\ \text{g}$ of the salt dissolves in $100\ \text{g}$ of water. The flask then stands in a cold room at $10\ ^\circ\text{C}$, where only $20\ \text{g}$ dissolves in $100\ \text{g}$ of water. What mass of salt is found as crystals?