You need to design a square toroid such that the magnetic field in the centre of the square windings is \(0.0020 \mathrm{~T}\), and the side length of a square winding is \(3 \mathrm{~cm}\). The wire you are using can carry a current of at most \(0.5 \mathrm{~A}\). The magnetic field anywhere inside the windings must be at least \(0.0016 \mathrm{~T}\). What is the minimum number of windings you will need?