複選題50、下列合金之主要成分，何者正確？ (A)青銅：鉛銅 (B)黃銅：鋅銅 (C)巴氏合金：錫銻銅 (D)蒙納合金：鎳銅。

10、 In Figure 10, a horizontal force of 500 N acts on a block of weight 1.5 kN placed on an inclined plane. The coefficients of friction between the block and the plane are μs =0.25 andμk = 0.20 . What is the actual frictional force? (A) 200N (B) 500 N (C) 300 N (D) 450 N。