(1) According to the meaning of the question, the stem and leaf diagrams of these two sets of data are as follows:

(2).X A = 85，。 X B = 85 (6 points)

S2 A = 15 [(82？ 85)2+(82? 85)2+(79? 85)2+(95? 85)2+(87? 85)2]=3 1.6

S2 B = 15 [(95？ 85)2+(75? 85)2+(80? 85)2+(90? 85)2+(85? 85) 2] = 50 (10 point)

∵.X A =。 x B，S2 A < S2 B

∴ A's grades are relatively stable, so send an A. (12 points)