## help me with this inequality

for positive reals a,b,c,d
show that
$\frac{b(c+a)}{c(a+b)}+\frac{c(b+d)}{d(b+c)}+\frac{ d(c+a)}{a(c+d)}+\frac{a(d+b)}{b(d+a)}\geq 4$