Why are NAND gates known as universal, and what is the advantage of a universal gate?

<ol><li><span style=”color:rgb(5,5,5);”> Why are NAND gates known as universal, and

what is the advantage of a universal gate?</span></li><li><span style=”color:rgb(5,5,5);”>why are DeMorgan’s theorems important?</span></li><li><span style=”color:rgb(5,5,5);”>Why do computers use binary numbers?</span></li><li><span style=”color:rgb(5,5,5);”>describe why the 2’s complement system is the preferred method for expressing and using signed binary numbers.</span></li></ol>