how to solve

Question 14 Keep using the data set for this question and the next 2 questions: In the study of Schizophrenia, researchers measured the activity of the enzyme monoamine oxidase(MAO) in the blood platelets of 18 patients. The results (in moles) are as follow: 4.1 5.2 6.8 7.3 7.4 7.8 78 8.4 8.7 9.7 9.9 10.6 10.7 11.9 12.7 14.2 145 18.8 Construct a stem and leaf plot using the leaf unit as the tenth's digit with 5 leaf category per stem. What is the value of the increment? [answer should be in decimal form, rounded to 1 decimal place]