Let \( \lambda^{*} \) be the largest value of \( \lambda \) for which the function \( f_{\lambda}(x)=4\lambda x^{3}-36\lambda x^{2}+36x+48 \) is increasing for all \( x\in \mathbb{R} \). Then \( f_{\lambda^{*}}(1)+f_{\lambda^{*}}(-1) \) is equal to:
\( 36 \)
\( 48 \)
\( 64 \)
\( 72 \)
