Two components of a minicomputer have the following joint pdf for their useful lifetimes X and Y: f(x, y)= xe^−x(1+y)  for x≥0 and y≥0
0 Otherwise

a. What is the probability that the lifetime X of the first component exceeds 3?
b. What is the probability that the lifetime of at least one component exceeds 3?
c. Are the two lifetimes independent?

Lin is writing an equation to model the proportional relationship between y, the total cost in dollars of downloading videos from a website, and x, the number of videos downloaded. she knows that the total cost to download 3 videos was $12. her work to find the equation is shown below. joylin’s work step 1 k= 3/12= 0.25 step 2 y= 0.25x where did joylin make her first error?