[填空题]
Two snowcats tow a housin cmzngu shil.s9i:; /*g unit qjn7+m,kx n)wu44w as)yi1 ae7k ey i83ztpu2to a new location at McMurdo Base, Antarctica, as shown in Fig. 4-46. The k t+yw z4 )s7mj7i wuaa4),n qynpi1k2ue3x8esum of the forces $\overrightarrow{\mathbf{F}}_{\mathrm{A}}$ and $\overrightarrow{\mathbf{F}}_{\mathrm{B}} $ exerted on the unit by the horizontal cables is parallel to the line L , and $ F_{\mathrm{A}}=4500 \mathrm{~N} $. Determine $ F_{\mathrm{B}}$ and the magnitude of $ \overrightarrow{\mathbf{F}}_{\mathrm{A}}+\overrightarrow{\mathbf{F}}_{\mathrm{B}}$ .$F_B$ = $\overrightarrow{\mathbf{F}}_{\mathrm{A}}+\overrightarrow{\mathbf{F}}_{\mathrm{B}}$ =
