three vertical parallel wires, equal in length and in the same vertical plane jointly suppport a load of 15000 N. the middle wire is steel, and the two outer ones are brass, and each is 160mm^2 in section. after the wires have been so adjusted as each to carry 1/3 of the load a further load of 30000N, is added. find the stress in each wire and the fraction of the whole load carried by the steel wire. E for steel=200 Gpa and E for brass=0.8*80Gpa.