"Alexa wants to determine if the actual proportion of orders that are delivered late to the customers is different from the value reported by the initial data analysis. In a recent random sample of 200 orders, Alexa found that 12 orders are delivered late. To use a normal distribution in this scenario, which of the following conditions must be satisfied?"
a. Both n x Po and n x (1 - po) must be at least 10 where po is the null value for the population proportion.
b. Any two samples must be independent of each other.
c. There must be at least 10 observed successes and 10 observed failures in the sample.
d. The observations within the sample must be independent of each other.