If we say that the amortized running time of an operation in a data structure is f$($n$),$ then Which one of the following is incorrect?

Some indivisual operations may take more than f$($n$)$ time but the average, over the entire sequence of operations, is at most f$($n$).$

The actual running time is a random variable and the expected value of this random variable is at most f$($n$).$

The cost of a typical operation is at most f$($n$).$

A sequence of m operations takes at most mf$($n$)$ time