Consider a helical extension spring $($Figure $14\mathrm{.}12)$ of a shutter return of a small camera made of ASTM

A$228$ music wire with the following given numerical values: d$=0\mathrm{.}6$mm$,$D$=2\mathrm{.}4$mm$,$P$=6$N$,$G$=79$

GPa, $($r$\_($m$))\_($A$)=1\mathrm{.}2$mmA