Question $6$:

Three vertical, parallel, straight wires have their upper ends firmly secured and their

lower ends supporting a rigid horizontal bar with a weight of $5$ kN which causes the

same elongation in each wire. The first wire has a cross$-$sectional area of $15m{m}^2$ and

is made of steel. The second wire is made of copper and has a cross$-$sectional area

of $30m{m}^2.$ If the third wire is subjected to a load of $20$ kN it will result in an elongation

of $25$ mm over a length of $2\mathrm{.}5$ m $.$ The initial length of the wire is $2\mathrm{.}5$ m $.$ Determine the

load carried by each wire and the total elongation of the system $($EST $=200$ GPa and

ECU $100$ GPa