Solve all it and provide it clearly

Based on a careful work study in a company, the results shown in the following table have been observed. Task element 6 A B 1 2.4 0.9 0.5 1 2 3.0 0.9 0.6 2.90 Observation 3 4 2.8 2.5 1.0 0.7 1.90 0.4 1.2 1.1 5 2.6 3.10 0.5 4.49 3.2 1.2 0.3 Performance Rating 85 100 95 125 D Disregard 0.9 a) Compute the normal time for each work element. (9 marks) b) If the allowance for this type of work is 15%, what is the standard time? (1 mark) c) How many observations are needed for a 95% confidence level within +5% accuracy for task element D