1. Build your 2:4 Decoder using two inverters and four AND gates

2. Build your NAND gate from a 2:4 Decoder

3. Build your 2-input 1 bit wide MUX exclusively from NAND gates

4. Build your 4-input 1 bit wide MUX from two 2-input 1 bit wide MUXs

5. Build your 8-input 1 bit wide MUX from two 4-input 1 bit wide MUXs and a 2-input 1 bit wide MUX

6. Build your XOR gate from an 8-input 1 bit wide MUX.

7. Build a 3 input XOR gate.