$($AND$-$XOR as universal logic $-15$ points$)$ In class, we have seen that NAND and NOR logic are universal.

a$)$ Similar to this prove or disprove that AND$-$XOR logic is also universal $($in the sense that any Boolean

function can be implemented with ANDs and XORs$).$

b$)$ Implement the logic function $f(a,b,c)=*b+ac$ using $2-$input AND and XOR gates.