A BWR fuel assembly has a $5*5$ square lattice with rod diameter of $10\mathrm{.}2$ mm and channel box inner width of $67\mathrm{.}7$ mm$.$ Most of the fuel rods have full length of $3\mathrm{.}7$ m$.$ Two rods have length of $1\mathrm{.}6$ and another two rods have length of $2\mathrm{.}72$ m$.$ All the fuel rods have the same inlet level at the bottom of the fuel assembly. The reactor operates at pressure of $7$ MPa with uniform rod surface heat flux, and the mass flux at the lower part of the fuel assembly is $1,260$ kg$/$m$2$s$.$ The inlet subcooling is $10\mathrm{.}8$ C and the exit quality is $0\mathrm{.}34.$ There are $7$ uniformly distributed spacers with interval of $0\mathrm{.}5$ m and the first spacer is located at $0\mathrm{.}5$ m from the inlet. The wet wall has roughness of $0\mathrm{.}0023$ mm and the spacer loss coefficient is $1\mathrm{.}95$ Re$-0\mathrm{.}08.$

Calculate the total pressure drop from inlet to outlet of the fuel assembly.

Justify the methods and models you used in each step $($for example, you can use HEM and WAM models$).$