A statistics practitioner would like to estimate the mean driving speed along the PIE, a major expressway in Singapore, during a typical heavy rain to within x km/hr. For a particular level of confidence and a given standard deviation of driving speeds, he uses a sample size of 800 cars for this study. Assuming there is no change in the confidence level required for this study, determine the statistician's new sample size if he now:

1. wishes his estimate to be double the accuracy of his original estimate.
2. halves both the given standard deviation of driving speeds and the accuracy of his original estimate.