4- In a study on the physical activity of young adults, pediatric researchers measured overall physical activity as the total number of registered movements (counts) over a period of time and then computed the number of counts per minute (cpm) for each subject (International Journal of Obesity, Jan. 2007). The study revealed that the distribution of the overall physical activity of obese young adults is approximately Normal with a mean of 320 cpm and a standard deviation of 100 cpm. (sketch an appropriate graph for each part) a) Find the interquartile range for the distribution of the overall physical activity of obese young adults. [ 5 marks] b) Which interval contains the central 80% of the the overall physical activity of obese young adults? [5 marks]