The feed$-$forward network shown below uses bipolar neurons, and maps the entire plane $x_1,x_2,$ into a bipolar value. Find the segment of the plane for which $y_4=1.$ NOTE: the neurons in the first computational layer have the neuronal $($activation$)$ function shown below. The neuron in the output layer is an MP neuron.

$f(y_{in})=\{\begin{array}{ccc}+1,& if& y_{in}0\\ -1,& if{y}_{-}in& <mn\; id="EditorElement\_3910890">0</mn>\end{array}$