Consider a computer with two-level cache system $L_{1}$ and $L_{2}$ along with a main memory $M$. The $L_{1}$ cache is divided into two parts: I-cache (Instruction cache) and $D$-cache (Data cache). The probability that the processor reads a memory for an instruction is $1 / 4$ and a data is $3 / 4$. The miss ratio of $D$-cache is two times of the miss ratio of the $L_{2}$ cache, but the miss ratios of $I$-cache and $L_{2}$ cache are the same. Let the access times of $I, D, L_{2}$ and $M$ be $4 \mathrm{~ns}, 4 \mathrm{~ns}, $40$ \mathrm{~ns}$ and $400$ ns , respectively. Let the average memory access time be $11$ ns . Compute the hit ratio of the $D$-cache.
