In the given diagram all are NOR Gate . The final output is shown in the figure. At stage 1 the output will be \overline A \& \overline B At stage 2 the output will be \overline {\overline A + \overline B } = A.B And the final output will be \overline {A.B} Hence for input A & B the output is \overline {AB} in case of Nand gate.
Galvanized steel conductors do not corrode, and possess high resistance. Hence such Wires are used in telecommunications circuits, earth wires, guard wire, stray wire, etc.