Answer:
[tex]a. \hspace{3} P(A\bigcap B) = \frac{3}{4}\\\\b. \hspace{3} P(A\bigcup B) = \frac{47}{50}\\\\c. \hspace{3} P(A'\bigcup B) = \frac{17}{20}\\\\[/tex]
Step-by-step explanation:
The information is configured in a double entry table in which the finishing information for the edge and surface is recorded, thus:
[tex]\begin{array}{cccc}&E&B&Total\\E&75&4&79\\B&15&6&21\\&90&10&100\\\end{array}[/tex]
Let A denote the event that a sample has excellent surface finish, and let B denote the event that a sample has excellent edge finish.
[tex]a. \hspace{3} P(A\bigcap B) = \frac{75}{100} = \frac{3}{4}\\\\b. \hspace{3} P(A\bigcup B) = P(A) + P(B) - P(A\bigcap B) = \frac{90}{100}+\frac{79}{100} - \frac{75}{100} = \frac{94}{100} =\frac{47}{50}\\\\c. \hspace{3} P(A'\bigcup B) = P(A') + P(B) - P(A'\bigcap B) = \frac{10}{100}+\frac{79}{100} - \frac{4}{100} = \frac{85}{100} =\frac{17}{20}\\\\[/tex]