The following concrete strength data (in ksi) were collected using an ultrasonic nondestructive testing method at different locations of an existing structure: 3·5, 3·2, 3·1, 3·5, 3·6, 3·2, 3·4, 2·9, 4·1, 2·6, 3·3, 3·5, 3·9, 3·8, 3·7, 3·4, 3·6, 3·5, 3·5, 3·7, 3·6, 3·8, 3·2, 3·4, 4·2, 3·6, 3·1, 2·9, 2·5, 3·5, 3·4, 3·2, 3·7, 3·8, 3·4, 3·6, 3·5, 3·2, 3·6, and 3·8· Plot a histogram and a frequency diagram for concrete strength·