need help STATS
For a certain section of pine forests , the number of diseased tree per acre ,X has a poisson distribution with mean equal to 9.The diseased tree are sprayed with an insecticide at a cost of R2.00 per tree ,plus a fixed overhead cost for equipment rental of R60.00.Letting Y denote the total spraying cost per acre.Suppose the forester wants the total spraying cost Y tobe within 2 units of the population mean at least 75% of the time .what is the largest value of the standard deviation of Y, the variance of Y that can be tolerated if the forester's objectives are to be meet.

Question

need help STATS
For a certain section of pine forests , the number of diseased tree per acre ,X has a poisson distribution with mean equal to 9.The diseased tree are sprayed with an insecticide at a cost of R2.00 per tree ,plus a fixed overhead cost for equipment rental of R60.00.Letting Y denote the total spraying cost per acre.Suppose the forester wants the total spraying cost Y tobe within 2 units of the population mean at least 75% of the time .what is the largest value of the standard deviation of Y, the variance of Y that can be tolerated if the forester's objectives are to be meet.