$=0.6*40 + 0.4*0.5(40+50*2) +0.4*0.5(40+ 50*2 + 150*4)$
$=24 + 0.2(140) + .2(740)$
$=24 + 28 + 148$
$= 200$ ns
Note that, on a miss in L1 and L2, blocks will be transferred from one level to next level.
PS: As pic quality is low so i assumed that respective hit ratios are 0.6, 0.5 and 1.