You are riding an elevator. Your fellow rider is nice and intelligent young woman. However, she never took any finance or economics classes during her college years. She asks you to explain what duration is. The ride is short, you have 15 seconds to think and 5 sentences to answer.

She also tells you that she is:

A. mathematician,

B. scientist

C. artist

Write 3 different explanations for each case in 5 sentences.