GATE CS 2025 Set 1 Q43 — Memory Hierarchy: Cache, Main Memory and Secondary Storage

A computer has a memory hierarchy consisting of two-level cache $\text{(L1}$ and $\text{L2)}$ and a main memory. If the processor needs to access data from memory, it first looks into $\text{L1}$ cache. If the data is not found in $\text{L1}$ cache, it goes to $\text{L2}$ cache. If it fails to get the data from $\text{L2}$ cache, it goes to main memory, where the data is definitely available. Hit rates and access times of various memory units are shown in the figure. The average memory access time in nanoseconds $(n s)$ is ________. (rounded off to two decimal places)