● 某计算机的时钟频率为400MHz，测试该计算机程序使用4种类型的指令。每种指令的数量及所需指令时钟数（CPI）如下表所示，则该计算机的指令平均时钟数约为 （4） 。 <table style="border: currentColor; border-image: none; margin-left: 5.4pt; border-collapse: collapse;" border="1" cellspacing="0" cellpadding="0" _dj="MsoNormalTable"><tbody><tr style="height: 28.1pt;"><td width="110" style="padding: 0cm 5.4pt; border: 1pt solid windowtext; border-image: none; width: 82.8pt; height: 28.1pt;">指令类型</td><td width="166" style="border-width: 1pt 1pt 1pt medium; border-style: solid solid solid none; padding: 0cm 5.4pt; width: 124.2pt; height: 28.1pt;">指令数目（条）</td><td width="180" style="border-width: 1pt 1pt 1pt medium; border-style: solid solid solid none; padding: 0cm 5.4pt; width: 135pt; height: 28.1pt;">每条指令需时钟数</td></tr><tr style="height: 22.1pt;"><td width="110" style="border-width: medium 1pt 1pt; border-style: none solid solid; padding: 0cm 5.4pt; width: 82.8pt; height: 22.1pt;">1</td><td width="166" style="border-width: medium 1pt 1pt medium; border-style: none solid solid none; padding: 0cm 5.4pt; width: 124.2pt; height: 22.1pt;">160000</td><td width="180" style="border-width: medium 1pt 1pt medium; border-style: none solid solid none; padding: 0cm 5.4pt; width: 135pt; height: 22.1pt;">1</td></tr><tr style="height: 22.35pt;"><td width="110" style="border-width: medium 1pt 1pt; border-style: none solid solid; padding: 0cm 5.4pt; width: 82.8pt; height: 22.35pt;">2</td><td width="166" style="border-width: medium 1pt 1pt medium; border-style: none solid solid none; padding: 0cm 5.4pt; width: 124.2pt; height: 22.35pt;">30000</td><td width="180" style="border-width: medium 1pt 1pt medium; border-style: none solid solid none; padding: 0cm 5.4pt; width: 135pt; height: 22.35pt;">2</td></tr><tr style="height: 23.3pt;"><td width="110" style="border-width: medium 1pt 1pt; border-style: none solid solid; padding: 0cm 5.4pt; width: 82.8pt; height: 23.3pt;">3</td><td width="166" style="border-width: medium 1pt 1pt medium; border-style: none solid solid none; padding: 0cm 5.4pt; width: 124.2pt; height: 23.3pt;">24000</td><td width="180" style="border-width: medium 1pt 1pt medium; border-style: none solid solid none; padding: 0cm 5.4pt; width: 135pt; height: 23.3pt;">4</td></tr><tr style="height: 23.65pt;"><td width="110" style="border-width: medium 1pt 1pt; border-style: none solid solid; padding: 0cm 5.4pt; width: 82.8pt; height: 23.65pt;">4</td><td width="166" style="border-width: medium 1pt 1pt medium; border-style: none solid solid none; padding: 0cm 5.4pt; width: 124.2pt; height: 23.65pt;">16000</td><td width="180" style="border-width: medium 1pt 1pt medium; border-style: none solid solid none; padding: 0cm 5.4pt; width: 135pt; height: 23.65pt;">8</td></tr></tbody></table>