Question 457932

According to question, defective lights should be found in 4th and 5th trail.

so, sequence should be :  non-defect, non-defect, non-defect, defect and defect.

2 defective , 8 non-defective, i.e total 10 

probability = 8/10 * 7/9 * 6/8 * 2/7 * 1/6 

= 1/45