Draw a graph showing scale factor versus time using the following data for redshifts and lookback times: At z = 0, tlb = 0; z = 1/3, tlb = 12; z = 1, tlb = 21; z = 1.5, tlb = 24; z = 3, tlb = 28; z = 9, tlb = 31. The units are arbitrary. Locate these data points on the graph and then draw a freehand curve through them.