For the circuit shown below the output Fis given by

The Boolean function A+BC is a reduced form of

For the identity AB+$$\overline A $$ C + BC= AB + $$\overline A $$ C, The dual form is

Implement the function $$F=\left(\overline A+\overline B\right)\left(\overline C+\overline D\right)$$ using two open collector TTL 2-input NAND gates.