Find the constant \(k\) for which the system with transfer function \(T(s)\) has the given second order response property.
(a) \(\mathrm{T}(\mathrm{s})=\frac{10}{s^{2}+40 s+k}, \quad \xi=0.7\)
(b) \(\mathrm{T}(s)=\frac{s^{2}-6}{k s^{2}+s+6}, \quad \omega_{n}=0.7\)