Every laptop returned to a repair center is classified according its needed repairs: (1) LCD screen, (2) motherboard, (3) keyboard, or (4) other. A random broken laptop needs a type i repair with probability pi = 24-i /15. Let Ni equal the number of type i broken laptops returned on a day in which four laptops are returned.
(a) Find the joint PMF
![](https://test.transtutors.com/qimg/488d52ba-7101-4397-acb0-95d8d07e7c36.png)
(b) What is the probability that two laptops require LCD repairs?
(c) What is the probability that more laptops require motherboard repairs than keyboard repairs?