## Discussion Forum

Que. | Let S be a stack of size n ≥ 1. Starting with the empty stack, suppose we push the first n natural numbers in sequence, and then perform n pop operations. Assume that Push and pop operation take X seconds each, and Y seconds elapse between the end of one such stack operation and the start of the next operation. For m ≥ 1, define the stack-life of m as the time elapsed from the end of Push(m) to the start of the pop operation that removes m from S. The average stack-life of an element of this stack is |

a. | n (X + Y) |

b. | 3Y + 2X |

c. | n (X + Y) - X |

d. | Y + 2X |

Answer:n (X + Y) - X |