A carriage spring 800 mm long is required to carry a proof load of 5000 N at the centre. The spring is made of plates 80 mm wide and 7.5 mm thick. If the maximum permissible stress for the material of the plates is not to exceed 190 MPa. Determine: The number of plates required. 2. The deflection of the spring, and 3. The radius to which the plates must be initially bent. The modulus of elasticity may be taken as 205 kN/mm2.