A truncation error X is uniformly distributed over the interval (0, 10^-20).

1. Write down the PDF of X.
2. What are its mean and variance!
3. Find P<0.2 10^-20 < X < 0.6 10^-20%.
4. For a summation of 10^7 independent terms subject to truncation, what are the mean, variance, and PDF of its total truncation error Y?