Consider a computer system that has cache memory, main memory $($RAM$)$ and disk, and an operating system that uses virtual memory. It takes $1nsec$ to access a word from the cache, $10nsec$ to access a word from the RAM, and $10ms$ to access a word from the disk. If the cache hit rate is $95\%$ and main memory hit rate $($after a cache miss$)$ is $99\%,$ what is the average time to access a word?