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Question $8$

$f$:$\{0,1\}4\{0,1\}4$

and $f(x)$

is obtained by replacing the first bit of $x$ with $1$

$.$ For example, $f(0100)=1100$

$.g$:$\{0,1\}4\{0,1\}4$

and $g(x)$

is obtained by removing the first bit of $x$ and placing a $0$

at the end. For example $g(0111)=1110$

Select the function that is well$-$defined.

a$.g.f$

b$.$f$.$g

c$.g-1.g$

d$.$f $-1.f$

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