All solutions here are SUGGESTED. Mr. Teng will hold no liability for any errors. Comments are entirely personal opinions.

(i)

Let number of calls in a period of 4minutes.

(ii)

Let length of time

Let number of calls in a period of minutes.

minutes

seconds

(iii)

Let number of calls in a working day of 12 hours.

Since approximately

by continuity correction

(iv)

Let number of busy days out of 6 working days.

(v)

Let number of busy days out of 30 working days.

Since is large,

approximately

by continuity correction

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