(b) The table below lists the USA social security costs in 7 different years between 1965 to 1992. Your aim is to fit the data with a simple regression model y = o + x + . Year x: Year 1960 1965 1970 1975 1980 1985 1990 1992 5 10 15 20 25 30 32 186.4 246.5 285.1 y: social security cost ($ Billion) 17.1 29.6 63.6 117.1 i. Please state the model assumptions. ii. Write down your fitted model (i.e. give the values of o and B). iii. Test the hypothesis Ho B = 0 against H >0. What can be concluded on the social security costs from the test? [Equal weight to each part; 20 marks in total]