heiarchical acces method is used why ?? "If the referenced block is not in L1,then transfer from L2 to L1,If not in L2,then transfer from L3 to L2 to L1".
$T avg= H1(L1)+(1-H1)(H2)(L1+L2)+(1-H1)(1-H2)H3(L1+L2+L3) =0.7(20)+0.3*0.9(200+20)+0.3*0.1*1(800+200+20) =14+59.4+30.6 =104nsec$
l2 access time is 200 nsec
L3 access time is 800 nsec
since they told block is transfered.