Ex.15 Neural Network

$$ \begin{aligned} h_{nj}^{(1)} &= \text{sigmoid}\left(\sum_{i=1}^mx_{ni}w_{ji}^{(1)} + b_j^{(1)}\right)\\ \vdots\\ h_{nj}^{(l)} &= \text{sigmoid}\left(\sum_{i}h_{ni}^{(l-1)}w_{ji}^{(l-1)} + b_j^{(l-1)}\right)\\ y_{nj} &= \text{softmax}_j\left(\right) \end{aligned} $$