Question

Consider a user types a document with a speed of 100 words
per minute. Assume that an average word consists of 5 letters and ends
by a break which can be a space, new line, TAB, or punctuation, and an
average sentence consists of 20 words. Assume that a spell-check thread
is only activated when a word break is detected, and it will finish its
task within 1 millisecond. Similarly, a grammar-check thread is only
activated when a sentence break, a period, is detected, and it needs 1.5
millisecond to finish its task. Assume that context switch overhead is 0.1
millisecond. What’s the maximum number of word processing users can
be admitted if the human eye refreshing rate is 1/20 second.