Answer:
The confidence interval is

Explanation:
From the question we are told that
The sample mean is

The standard deviation is

The sample size is

given that the confidence level is 85% then the level of significance is mathematically represented as

Next we obtain the critical value of
from the normal distribution table the value is

Generally the margin of error is mathematically represented as

=>

=>

The 85% confidence interval is mathematically represented as

=>

=>
