Money cannot buy happiness. Or can it? The populations of some countries are happier than other countries. In this exercise, you will investigate the relationship between a country's per capita GDP and its "happiness score". Since 2012, the annual World Happiness Report, published by the United Nations' Sustainable Development Solutions Network, asks people around the world how happy they are. The happiness score uses the Cantril scale, which is a subjective scale constructed by asking respondents to imagine a ladder on which the best possible life for themselves receives the score of 10, the worst possible life a score of 0, and then are asked to rate their own lives on that scale between 0 and 10. The questionaire is given to a representative sample of each country each year. We expect more individual wealth to correlate with higher happiness. But, how much of the variation in happiness is explained by individual wealth? That is the question we will explore. There are three main tasks in this notebook. PART A. Implement Gradient Descent to calculate the coefficients of a univariate linear regression PART B. Use a built-in library to check your implementation in A and perform some analysis PART C. Prepare data yourself and apply your model. You will be asked to write some code and also answer several questions about the model and data. The first step is to run the next cell to load the basic libraries we will use in this assignment.