Answer Happy

a , b and c
l need thier solution please
Of the 30 used computers available in the stock of a certain firm 3 are not working prop- erly. Tlie firm sells 6 used computers, which are randomly selected from the 30. Suppose that a good computer (working properly) is installed in 2 minutes, and a defective one (not working properly) is installed in 15 minutes. (a) Find the probability that all 6 computers will working properly. (39 b) Find the expected value, and the standard deviation of the time T it will take to install these 6 computers. T=2x-15 (c) Find the shortest interval certain to contain at least 90% of the times M