The length of time (in years) until a particular radioactive particle decays is a random variable t with the probability density function by: f(t) = 0.03e^(-0.03t); for t in [0, infinity]find the mean of the distribution, the standard deviation of the distribution, and the probability that the random variable is between the mean and one standard deviation above the mean

What situation is an example of an observational study

Me because some of question i don’t understand

Barney & noblet customers can choose to purchase a membership for $25 per year members receive 10% off all store purchases 1. how much would a member pay per year if he bought $50 worth of items each year? 2. write a slope-intercept equation that expresses how much a member pays per year using x to represent his purchases per year 3. how much would a member have to spend per year to pay off his membership fee?