[tex]1)\\4\ different\ models,\ 3\ different\ colors\ and\ 2\ sizes\\\\4\cdot3\cdot2=24\ (choices)\\\\17.\\20\ entries\ in\ the\ chess\ tournam.\\\\20-the\ number\ of\ ways\ to\ select\ 1.\ places\\19-the\ number\ of\ ways\ to\ select\ 2.\ places\\18-the\ number\ of\ ways\ to\ select\ 3.\ places\\\\\ the\ number\ of\ ways\ to\ select\ the\ top\ three=20\cdot19\cdot18=6,840[/tex]