The probability is:
0.71
Let A denote the event it is defective
and B denote the event that it is not made by Ratten company.
Lens Defective Not Defective Total .
Greens 5% 55% 60% .
Parsons 10% 5% 15% .
Ratten 6% 19% 25% .
Total 21% 79% 100%
P(A)=0.21
( Since 21/100=0.21 )
P(A∩B)= 15%
( Since, 5%+10%=15%
and 15%/100%=0.15)
Hence, we are asked to find P(B|A)
We know that:
[tex]P(B|A)=\dfrac{P(A\bigcap B)}{P(A)}\\\\\\P(B|A)=\dfrac{0.15}{0.21}\\\\\\P(B|A)=\dfrac{15}{21}\\\\\\P(B|A)=0.71[/tex]
The answer is:
0.71