Two data sets of 23 integers each are summarized in the histograms shown. For each histogram, the first interval represents the frequency of integers greater than or equal to 10 but less than 20, the second interval represents the frequency of integers greater than or equal to 20 but less than 30, and so on.

Data Set A:
Interval [20,30): Frequency 3
Interval [30,40): Frequency 4
Interval [40,50): Frequency 7
Interval [50,60): Frequency 9

Data Set B:
Interval [10,20): Frequency 3
Interval [20,30): Frequency 4
Interval [30,40): Frequency 7
Interval [40,50): Frequency 9

If the value of each integer in both data sets is assumed to be the midpoint of its respective interval, what is the difference between the mean of data set A and the mean of data set B?