Question 2c involves analysing the data from a creep test. In Activity 18.1b you saw equations that described the relationship between creep strain and time for data extracted from a creep experiment similar to the one you observed in Study Week 17. You used the equations and your mathematical knowledge of calculus to calculate creep strain rate at different times during the creep experiment. The creep strain rate is the change in creep strain with respect to time. C. i. Explain in words how you can use differential calculus to calculate the creep strain rate from a set of data for creep strain as a function of elapsed time. State any standard rules for differentiation that you would need to apply in obtaining your result. Your answer should be no more than 200 words. You do not need to include equations, but you can include general equations and/or specific examples if it helps with your description. (5 marks) ii. The equation below is a polynomial of order 4, fitted to the data recorded in a creep test conducted on a particular type of steel, for an elapsed time between 10 to 20 hours. = 4 10 5 +4 -0.0024+3 + 0.04872 - 0.3429 + 1.453 The data were recorded for % strain versus elapsed time in hours. Use this equation to calculate the creep strain rate at 16 hours elapsed time. Give your answer to 1 significant figure. (5 marks) (Total for Question 2c = 10 marks)