Please help with 15, 39, 45, and 49. I do not understand how to complete these problems, explanations would be helpful.

15. The graph shows how the average surface water temperature f of Lake Michigan varies over the course of a year (where is measured in months with f = 0 corresponding to Janu- ary 1). The average was calculated from data obtained over a 20-year period ending in 2011. Sketch the graph of the derivative function f'. When is f'() largest? ACF) 70 60 50 40 10 12 / (months)39. Let / represent the percentage of a city's electrical power that is produced by solar panels / years after January 1, 2020. (a) What does dP/di represent in this context? (b) Interpret the statement dP = 3.545. Graph the function f(x) Ext . Zoom in repeatedly. first toward the point (-1, 0) and then toward the origin. What is different about the behavior of / in the vicinity of these two points? What do you conclude about the differen tiability of f?The figure shows the graphs of f, f', and f". Identify each curve, and explain your choices. C