by direct incpection
x=2.3 $\Rightarrow$ f(x)=1.8
x=2.5 $\Rightarrow$ f(x)=1.6
x=2.7 $\Rightarrow$ f(x)=1.8
now we can check value of f(x) before and after 2.5+$\alpha$, 2.5 - $\alpha$
x=2.5+$\alpha$ $\Rightarrow$ f(x)=1.6+$\alpha$ and
x=2.5-$\alpha$ $\Rightarrow$ f(x)=1.6+$\alpha$
so we can conclude that this is minimum value
Ans:2