The data show the number of murders in 25 selected cities.
Class limits Frequency
34–96 .........13
97–159 .........2
160–222 .......0
223–285 .......5
286–348 .......1
349–411 .......1
412–474 .......0
475–537 .......1
538–600 .......2
Find the variance and standard deviation.