A project company hired 800 casual employees to undertake a major housing project. On average (daily basis) these workers take 8 hours to complete a given task with a s.d deviation of 2 hours. If...

A project company hired 800 casual employees to undertake a major housing project. On average (daily basis) these workers take 8 hours to complete a given task with a s.d deviation of 2 hours. If completion time is normally distributed, determine the no. of workers who completed the task in: -

1. More than 13.5 hours


2. Between 6.5 hours and 14.5 hours


3. Between 2.5 hours and 5.8 hours