Assertion (A) : Cold working of metals result in increase of strength and hardness.
Reason (R) : Cold working reduces the total number of dislocations per unit volume of the material.

Consider the following statements:
In comparison to hot working, in cold working,
$$1.$$ Higher forces are required
$$2.$$ No heating is required
$$3.$$ Less ductility is required
$$4.$$ Better surface finish is obtained.

Which of the statements given above are correct?

A $$\phi \,\,25$$ $$mm$$ hole is pierced in a $$t=2.5mm$$ thick steel sheet having shear strength $$\tau = 350\,\,MPa.$$ If the diametral clearance is given by the expression $$C=0.0064$$ $$t$$ $$\sqrt \tau ,$$ the die diameter (in $$mm$$), punch diameter (in $$mm$$) and punch force in $$(kN)$$ respectively are

Ring gage is used to measure