Julie made 25 international long-distance phone calls to London last month. The scatterplot below shows the length and cost of each phone call she made. Which conclusion is best supported by the scatterplot? As the length of a call increases, the cost of the call remains the same. As the length of a call increases, the cost of the call increases. There is no relationship between the length of a call and the cost of a call. As the length of a call increases, the cost of the call decreases.

The biologist has a second culture to examine. she knows that the population of the culture doubles every 15 minutes. after 1 hour and 15 minutes, her assistant found that 80,000 bacteria were present. a) what was the size of the initial population? b) predict the size of the culture at t=3 hours. what was the size of the population at 40 minutes? explain and justify your answers. c) create a graph of the population as a function of time. find an equation that can be used to predict the size of the population at any time t. d) examine the rate at which the bacteria culture is growing. how fast is the culture growing after 1 hour? after 1.5 hours? after 2 hours? use a time interval of h = 0.01 hours to estimate these rates. interpret these rates in terms of the context of the problem situation. how do these three rates compare?