12.65 Five sheets of writing paper are randomly selected from each of three batches produced by a certain company. A measure of brightness is obtained for each sheet, with the results listed in table below.

a Do the mean brightness measurements seem to differ among the three batches? Use 0.05.
b If you were to select the batch with the largest mean brightness, which would you select?
Why?

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Batch 1 2 3 28 34 32 36 25 32 222 27 25 29 27 38 31 26 39 21