Problem 6 on HW 3.4

PhoneData={{0,8.70},{1,16.24},{2,37.04},{3,47.79}}

PhoneBestFitLine = LinearModelFit[PhoneData,{1,t},t]

PhonePlot =ListPlot[ {PhoneData}, PlotMarkers->{"X"}, PlotStyle->{Black}, PlotLegends->{"iPhone Sales"}, PlotLabel->"iPhone Sales since 2010",PlotRange->{{-1,4},{0,50}}];

LinePlot = Plot[PhoneBestFitLine[t],{t,-1,5},PlotStyle->{Blue,Thickness[0.005]},PlotLegends->{"Line of Best Fit"}];

Show[PhonePlot,LinePlot]

PhoneBestFitLine[6]