2.1 The reliability of any engineering system is based on the definition of failure and limit state function. Provide a definition of failure with reference to a practical example in an engineering field of your interest, e.g.,] civil/mechanical/system engineering. With reference to the same example, provide a possible limit state function in its possible formulations. 2.2 Define the probability of failure (Pf) considering both the Safety Margin and Safety Factor formulations. Address this point using diagrams and sketches if appropriate. 2.3 List the four possible levels of reliability analysis. Which of these levels are codes and guidelines based? What is the practitioner's approach?