Two helical coil springs are made from a steel (left(mathrm{E}=200 times 10^{9} mathrm{~N} / mathrm{m}^{2} ight)) bar

Two helical coil springs are made from a steel \(\left(\mathrm{E}=200 \times 10^{9} \mathrm{~N} / \mathrm{m}^{2}\right)\) bar with a radius of \(20 \mathrm{~mm}\). One spring has a coil diameter of \(7 \mathrm{~cm}\); the other has a coil diameter of \(10 \mathrm{~cm}\). The springs have 20 turns each. The spring with the smaller coil diameter is placed inside the spring with the larger coil diameter. What is the equivalent stiffness of the assembly?