Light impurities in the molten metal are prevented from reaching the mold cavity by providing a

A wire of $$0.1mm$$ diameter is drawn from a rod of $$15mm$$ diameter dies giving reductions of $$20\% $$, $$40\% $$ and $$80\% $$ are available. For minimum error in the final size, the number of stages and reduction at each stage respectively would be

Preheating before welding is done to