题目

Five couples have been living side by side on Beasley Street in Pearce for 45 years. In May 1968, five young couples moved into new houses there. Forty­five years later, they are still there, and although most are now retired and their children have left home, the neighbours remain good friends. Yesterday, they gathered at Mr. and Mrs. Miller’s house to share lunch, joined by relative (相对的) newcomers, the Browns, who moved there three decades ago. On either side of the Millers live the Blacks, the Greens, and the Whites. The only person missing the lunch was their neighbour, Kath 在Rt△ABC中，∠C=90°，AC=3，则AB•AC= ．