I1.2 If the solution of the inequality $2 x^{2}-a x+4<0$ is $1<x<b$, find $b$.
$\begin{array}{l}2 x^{2}-6 x+4<0 \\ \Rightarrow 2\left(x^{2}-3 x+2\right)<0 \\ 2(x-1)(x-2)<0 \\ 1<x<2 \\ \Rightarrow b=2\end{array}$