If 30 minorities apply, how many minorities should be hired to avoid an adverse impact claim?

Problem 1: An organization hired 50 non-minority management trainees, and their selection rate among qualified non-minority candidates was 25%.

Questions
1. If 30 minorities apply, how many minorities should be hired to avoid an adverse impact claim?
2. What federal statute governs this issue?

Problem 2: An organization received 100 employment applications from Caucasians for a position and found that 50 of them were qualified. Another 60 applications were received from Hispanics, of which 20 were qualified, and 30 applications from African-Americans, of which 10 were qualified. After interviewing the majority of the qualified candidates from all classes, 40 Caucasians, 16 Hispanics and 6 African-Americans were hired.

Questions
1. Does adverse impact exist against any of the protected classes in this group? If so, who, and by how much?
2. If adverse impact exists, does that make a prima facie case for discrimination? What must be done if does exist?