0 \leq \frac{\|f(h_1,h_2)\|}{\|(h_1,h_2)\|} \leq \frac{\displaystyle \sum_{i=1}^{n}\displaystyle \sum_{j=1}^{m}\|h_i^{(1)}h_j^{(2)}f(e_i, e_j)\|}{\|(h_1,h_2)\|}}=\frac{\displaystyle \sum_{i=1}^{n}\displaystyle \sum_{j=1}^{m}|h_i^{(1)}| |h_j^{(2)}| \|f(e_i, e_j)\|}{\sqrt{\displaystyle \sum_{k=1}^{n}(h_k^{(1)})^2+ \displaystyle \sum_{l=1}^{m}(h_l^{(2)})^2}} \\ \leq \frac{\displaystyle \sum_{i=1}^{n}\displaystyle \sum_{j=1}^{m}|h_i^{(1)}| |h_j^{(2)}| \|f(e_i, e_j)\|}{\sqrt{\displaystyle \sum_{k=1}^{n}(h_k^{(1)})^2}} \leq \displaystyle \sum_{i=1}^{n}\displaystyle \sum_{j=1}^{m}\frac{|h_i^{(1)}| |h_j^{(2)}| \|f(e_i, e_j)\|}{\sqrt{(h_i^{(1)})^2}}=\displaystyle \sum_{i=1}^{n}\displaystyle \sum_{j=1}^{m}|h_j^{(2)}| \|f(e_i, e_j)\|}