In an attempt to determine if two competing brands of cold medicine contain, on average, the same amount of acetaminophen, twelve different tablets from each of the two competing brands were randomly selected and tested for the amount of acetaminophen each contains the results (in milligrams) follow

Brand A 520 495 505 493 503 493 505 495 498 481 499 494

Brand B 490 508 514 521 541 533 500 516 536 498 515 515

a find a 95% confidence interval for the true mean value of acetaminophen for the two brands

b at a=0.05 is there enough evidence to reject the claim that the two medications have the same amount of acetaminophen