Design a post-tensioned simply supported beam with a span of 25 m that supports a characteristic load of 15 kN/m (excluding self-weight). Select one of the standard I sections. Use Magnel diagram for calculating the pre-stressing force and its eccentricity required at the mid-span. Use fck = 50 MPa, ftt = 0, fct = 20 MPa, fts = 0, fcs = 15 MPa, short-term losses 10%, and long-term losses 20%. Assuming that the pre-stressing strands are made of 7 wires with 8 mm diameter with the tensile strength of 1860 MPa, calculate how many strands will be required to make the pre-stressing cable.