11. A manufacturer receives parts from two suppliers. An SRS of 400 parts from supplier I finds 20defective. An SRS of 100 parts from supplier 2 finds 10 defective. Let pt and po be theproportion of all parts from suppliers I and 2, respectively, that are defective. A 95%confidence interval for p1 - p2is
(A) -.056±0.068.
(B) -.056±0.054.
(C) -.056±0.033.
(D) .056 ±0.033.