The number of Facebook users (in millions) was tracked between 2004 and 2011. (a) Visually assess the number of users. What pattern(s) does the time series exhibit? O a. Negative linear trend O b. Positive linear trend O c. Positive nonlinear trend O d. Negative nonlinear trend (b) Build a nonlinear trend regression model and provide the equation of the line fit O a. T. = 84.214-90.211t+ 19.3682+0.507613 O b. T.= -283.96+ 119.63t O c. T = 109.34-116.35t + 26.22+2 (c) What are the forecasted number of users for years 2012 and 2013? O a. 793 and 913, respectively O b. 1186 and 1568, respectively O c. 105908349 and 106013768, respetively O d. 857 and 1186, respectively