On a microcomputer hard disk, we count 400 files, each one consisting of eJ-zzactljir 50 records. To estimate the average number of characters per record, we decide to sample Bl} files using simple random sampling, then in each selected le, we sample 5 records using simple random sampling. After sampling we nd: I the variabilityr (or variance] of the total number of characters per file is 905001]; I the mean of the all 401} variances, where the ith variance is the variance of the number of characters per record in file 11,11: 11 , _ _ 1401]. is equal to 805. 3] Identify the sampling design to draw this sample. b] How do we estimate without bias the mean number 17;; of characters per record? {Find a general estimator and not an estimate] c] How do we estimate without bias the accurac}...r of the previous estimator? [Find both estimator and the numerical value.)