in a shipment of 20 computers, 3 are defective

Question

three computers are randomly selected and tested. what is the probability that all 3 are defective if the first and second ones are not replaced after being tested.

a. 1/760
b.1/1140
c.27/8000
d.3/5000

i chose D, is this correct

Answer 1

First one 3/20
Second one 2/19
third one 1/18
3/20*2/19*1/18 = 1/(3*20*19) =1/1140

Answer 2

The answer is B Explanation: 3/20*2/19*1/18=1/(3*20*19)=1/1140

Answer 3

In a shipment of 20 computers, 3 are defective. Two computers are randomly selected and tested. What is the probability that both are defective if the first and second ones are not replaced after being tested?