A first row transition metal with highest enthalpy of atomisation, upon reaction with oxygen at high temperature forms oxides of formula $\mathrm{M}_2 \mathrm{O}_{\mathrm{n}}$ (where $\mathrm{n}=3,4,5$). The 'spin-only' magnetic moment value of the amphoteric oxide from the above oxides is _________ $\mathrm{BM}$ (near integer)

(Given atomic number: $\mathrm{Sc}: 21, \mathrm{Ti}: 22, \mathrm{~V}: 23, \mathrm{Cr}: 24, \mathrm{Mn}: 25, \mathrm{Fe}: 26, \mathrm{Co}: 27, \mathrm{Ni}: 28, \mathrm{Cu}: 29, \mathrm{Zn}: 30$)