[填空题]
The americium nucleutc3h *o yrzv2+-0tm)fvic3 wkvqs cx0nyx8 h45b:d/fs, $^{241}\text{Am}$, decays to a neptunium nucleus, $^{237}\text{Np}$, by emitting an alpha particle of mass 4.00260 u and kinetic energy 5.5 MeV. Estimate the mass of the neptunium nucleus, ignoring its recoil, given that the americium mass is 241.05682 u. $m_{Np}$ = u
