Match the application with type of pattern

The primary function of a riser is to

Two sheets of low carbon steel $$1.5mm$$ thick each are spot welded by passing a current $$10000$$ amps for $$5$$ cycles in $$50$$ $$Hz$$ main supply.

i) What is the heat generated due to the supply of power if effective resistance has $$200$$ micro ohms,

ii) The maximum indentation is $$10\% $$ of sheet thickness and density of the spot weld nugget $$8$$ $$gm/cc.$$ If $$1380$$ Joules are required to melt $$1gm$$ of steel, determine heat required for welding operation if $$D=6SQRT$$ $$(t)$$ to determine nugget diameter $$D$$ and assume the nugget size to be equal to metal between the two electrodes

The type of coated electrode most widely used for welding low carbon steel is