A certain spring is found not to conform to Hooke's law. The force it exerts when stretched a distance $\backslash ($ x $\backslash )$ is found to have magnitude $\backslash (60\mathrm{.}0$ x$+43\mathrm{.}8$ x$^\{2\}\backslash )$ in the direction opposing the stretch, where force is in Newtons and deformation is in meters. The original length of the spring is $0\mathrm{.}273$ m $.$

A$.$ Calculate the spring force necessary to stretch the spring to a length of $0\mathrm{.}411$ m $.$

B$.$ Calculate the work necessary to stretch the spring to a length of $0\mathrm{.}411$ m $.$

C$.$ Calculate the work required to stretch the spring from $0\mathrm{.}411$ m to $0\mathrm{.}754$ m $.$

D$.$ With one end of the spring fixed, a of mass $2\mathrm{.}07$ kg is attached to the other end of the spring when it is stretched to $0\mathrm{.}754$ m $.$ If the mass is then released from rest, compute its speed at the instant the spring has returned to a length of $0\mathrm{.}411$ m $.$