Amortized analysis of stacks. There is a stack with three operations: push, pop, and multipop$($k$).$ The multipop$($k$)$ operation is implemented as a series of k pops. push and pop each take $1$ unit of time, and multipop$($k$)$ takes k unit of time. Using amortized analysis, we determined that the average cost of an operation, over n operations, was $2$ units of time.