Two fuel additives are being tested to determine their effect on petrol mileage. Eight cars were tested with additive I and ten cars were tested with additive II. The following table shows the petrol mileage (kilometres per litre) from the two additives. Assume that the petrol mileage from both additives are normally distributed with unknown means and variances. Further assume that both additives have equal yariances (i) Construct a 95% confidence interval of the difference in mean petrol mileage of both additives. (ii) At the 5% significance level, test the hypothesis that the mean petrol mileage of additive I is less than that of additive II..