On the opening day at a toy store every third customer gets a ball and every fourth customer gets a stuffed animal sixty people come to the store how many get both a ball and stuffed animal

At the beginning of a call to the cable company, a message tells customers, "after you finish talking to our customer service representative, you will be asked to take a five-question survey about the level of service you recieved. it would be appreciated if you could stay on the line to answer the survey questions." what type of sampling is the cable company using?