4.1 The percentage extension () after time t (s) under true stress o (MPa) of a homopolymer is given with the following equation. = 0.0660 + 1.5.10-6.t/3. e0.60t a) Plot o against at fixed times t = 1 s and 1000 s, and hence determine the nominal yield stress for each time. Hint: Calculate & values at 1s and 1000s for 5, 10, 15, 20, 25, and 30 MPa. You can use excel and tabulate values. b) Calculate an equivalent strain rate corresponding to each yield stress by dividing yield strain by time to yield.