$1\mathrm{.}6.$ A frame is formed by two metallic rectangular cross sectional parts soldered along their inclined planes as illustrated in Fig. P$1\mathrm{.}6.$ What is the permissible axial load $P_{\text{a}\text{l}\text{l}}$ that can be applied to the frame, without exceeding a normal stress of ${}_{\text{a}\text{l}\text{l}}$ or a shearing stress of ${}_{\text{a}\text{l}\text{l}}$ on the inclined plane? Given: $a=10mm,b=75mm,t=20mm,=55,{}_{\text{a}\text{l}\text{l}}=25$MPa, and ${}_{\text{a}\text{l}\text{l}}=12$MPa. Assumption: Material strength in tension is $90$ MPa $.$

Figure P$1\mathrm{.}6.$