General Formula for a Parameterized Function

A machine learning model is designed to predict a property's value based on four input features: square footage, number of bedrooms, age of the building, and lot size. Using the standard convention for representing a finite set of indexed variables, how would this set of inputs be denoted?

A function is designed to process a set of inputs represented by the notation ({x_0, x_1, \dots, x_{9}}). Based on this notation, the function takes a total of ______ input variables.

In the standard notation for a finite set of indexed variables, ({x_0, x_1, \dots, x_m}), the letter m represents the total number of variables in the set.