Let \(\displaystyle g(x)=3\,f\!\left(\frac{x}{3}\right)+f(3-x) \) and \( f''(x)>0 \) for all \( x\in(0,3) \). If \( g \) is decreasing in \( (0,\alpha) \) and increasing in \( (\alpha,3) \), then \( 8\alpha \) is:
\( 18 \)
\( 24 \)
\( 0 \)
\( 20 \)