(a)In the context of measuring cost of workers' work related injuries, the following data are provided:

Average cost per worker $32,000 with standard deviation $9,500. Assuming that the data are normally distributed,

Find the proportion of the costs that are between $4,500 and $21,000.

(ii) Suppose the standard deviation is unknown, but 88% of the costs are more than $7,500,

what should be the value of the standard deviation?