Question 144
Let $a$, $b$, $c$ be positive real numbers with $a b c = 1$. Determine all possible values that the expression
$$
\frac{1+a}{1+a+a b} + \frac{1+b}{1+b+b c} + \frac{1+c}{1+c+c a}
$$
can accept.
$$
\frac{1+a}{1+a+a b} + \frac{1+b}{1+b+b c} + \frac{1+c}{1+c+c a}
$$
can accept.