When the running time of algorithm A is T$($n$),$ and T$($n$)=$ O$($f$($n$)),$ then which of the following statements is NOT correct?

The running time of algorithm A is O$($f$($n$)).$

There exists c $>0,$ and n$0$ such that T$($n$)<=$cf$($n$)$ for all n$>=$n$0$

T$($n$)=$O$($n$)$

T$($n$)$ in O$($f$($n$))$