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

The cross section weld bead is shown in fig the profile of the bead and the fusion zone are taken circular for convenience. Bead width and radii of curvature of circular profiles are given in fig. The bead height and depth of penetration are