5.4. The probability density function of X, the lifetime of a certain type of electronic device, is given by and a) Find P(X > 20). b) What is the cumulative distribution function of X? c) What is the probability that of 6 such types of devices, at least 3 will function for at least 15 hours? What assumptions are you making?

3rd box is the answer

step-by-step explanation:

the correct answer is b. negative exponential growth.

step-by-step explanation:

you can tell it's an exponential function because it decreases rapidly then levels out and never touches the x-axis.

it is negative because the y-axis decreases as the x-axis increases.

therefore it is a negative exponential growth graph.

hope i !