A computer system has a L$1$ Data Cache, L$2$ Data Cache, and Main Memory unit connected as shown in

the diagram. For a Program the Data hit rate in L$1$ and L$2$ Data Cache is H$1$ and H$2$ respectively $($both H$1,$ H$2$

are specified as a percentage$).$ The time to access the data in L and L$2$ Data Cache is T$1$ and T$2$ ns

respectively. The time to Access the Main Memory is T$3$ ns$.$

Note: The time to access L$2$ Data cache T$2$ includes the time to L$1$ Data Cache. So the time to access L$2$ should

not be assumed as T$1+$ T$2$ ns$.$ Similarly the time to access Main Memory is T$3$ ns and should not be assumed T$1$

$+T2+T3ns$

$H1=80$

$H2=40$

$T1=10$

$T2=30$

$T3=100$

The average Data Access time in ns is