The D family consists of Mr. and Mrs. D and Mrs. D's aged, invalid father. As usual D prepares pre-dinner drinks - martinis for his wife and father-in-law and a highball for himself. Since it is a special occasion, D also prepares hors d'oeuvres. But D does not eat any hors d'oeuvres himself. The next day his wife and father-in-law are found dead. An autopsy of the bodies and a chemical analysis of the martinis and hors d'oeuvres reveal traces of arsenic poisoning in the bodies, drinks, and food. D is charged with two counts of first-degree murder. 

(a) At D's trial suppose that the prosecution proves the above and then calls W, a salesman in the local drugstore, to testify that on December 24 he sold D a tube of rat poison. On D's objection, what ruling and why? 

(b) Suppose the prosecution calls S, W's sister, to testify that W told her on December 25 that D bought rat poison. On D's objection, what ruling and why?