To find the mean number of calls per minute, we need to calculate the sum of the products of the number of calls and their corresponding frequencies, and then divide by the total number of intervals.

Number of Calls: 0 1 2 3 4 5 6 7 Frequency: 14 21 25 43 51 40 39 12

Sum of products = (014) + (121) + (225) + (343) + (451) + (540) + (639) + (712) = 0 + 21 + 50 + 129 + 204 + 200 + 234 + 84 = 922

Total number of intervals = 245

Mean number of calls per minute = Sum of products / Total number of intervals = 922 / 245 = 3.76

Therefore, the mean number of calls per minute is 3.76.