We have given the number of successes and the sample size for a simple random sample from
a population. In each case, do the following tasks.
a. Determine the sample proportion.
b. Decide whether using the one-proportion z-interval procedure is appropriate.
c. If appropriate, use the one-proportion z-interval procedure to find the confidence interval at the specified confidence level.
$$x=10, n=40,90 \% \text { level. }$$