4. (Table available in the Excel file) The time required (in months) to prepare for a high endurance race among elite athletes can vary depending on different conditions, i.e., health status, dietary requirements, specific physical training, etc. The table below shows the probability of elite athletes being considered fully prepared for one endurance race after meeting specific performance metrics. a. What is the mean time for athletes to be considered fully prepared? b. Calculate standard deviation and variance. What is the standard deviation telling us regarding the preparation time for athletes? 5. The diameter of a rivet (in mm ) is a random variable with probability density function: f(x)={6(x12)(13x)012