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a$)$ What is Kronecker delta?

b$)$ A $3-$mm$-$long gold alloy wire intended to electrically bond a computer chip to its package has an initial diameter of $30m.$ During testing, it is pulled axially with a load of $15$ grams$-$force. If the wire diameter decreases uniformly to $29m,$ compute the following:

$($i$)$ The final length of the wire.

$($ii$)$ The true stress and true strain at this load.

$($iii$)$ The engineering stress and strain at this load.