1: Describe the unique challenges that time series applications present when considering how we split our data into training and validation (test and safe) sets. 

Problem 2: Identify each of the following applications as time series or not. Be sure to justify your choice. 

a) Predicting customer volume from week to week for a restaurant. 

b) Predicting the selling price of a home using the selling prices of comparable homes over the last two months. 

c) Predicting the starting salary of an individual based off of their gender, number of years of schooling, highest degree attained, and number of years of relevant work experience.