Propose a structure for an amine of formula C4H9N, which does not liberate a gas when treated with NaNO2 and HCl, and has IR absorptions at 917 cm-1, 990 cm-1, and 1640 cm-1, as well as an N-H absorption at 3300 cm-1. The CNMR spectrum is 36.0, 54.4, 115.8, 136.7. Draw C4H9N.