A server accepts and processes requests from clients. The server keeps the results of the most recent requests in memory as a cache.

$$ A new request arrives on average every $10$ ms$.$

$$ The processing of each request takes $5$ ms$.$

$$ If the requested result is not in the memory cache, additional $15$ ms are needed to access the disk.

$$ On average, $65\%$ of all requests can be serviced without disk access.

$$ The creation of a new thread takes $2\mathrm{.}5$ ms$.$

Should the server be implemented as a single$-$threaded or a multi$-$threaded process? Justify your answer.

$[2$ points $]$