2015 ONE(e)

Salt harvested at the Grassmere Saltworks forms a cone as it falls from a conveyor belt.
The slant of the cone forms an angle of $30^{\circ }$ with the horizontal.
The conveyor belt delivers the salt at a rate of $2{\mathrm{m}}^3$ of salt per minute.

Find the rate at which the slant height is increasing when the radius of the cone is $10\mathrm{m}$.
*You must use calculus and show any derivatives that you need to find when solving this
problem.*