A scientist is interested in the average height of all plants of a particular type treated with an

A scientist is interested in the average height of all plants of a particular type treated with an experimental chemical. She wants to be 90% confident that her interval will contain the true mean but doesn’t want her error to be larger than 1cm. A prior pilot study suggests that 5.35cm is a reasonable value for the standard deviation in height. How many plants should she sample for treatment with the chemical? Note: you may assume the Central Limit Theorem applies here