You also need an estimate of the number of new subscribers in 2000. First, choose an estimate of new subscribers per month. One way to get this is to use the number of new subscribers in March, 2000, given in the case. There were roughly 155,000 total subscribers as of the end of March, 2000, and the case gives you an estimate of the number of paying subscribers at that point, so the difference must be the number of new subscribers during that month. Take either this estimate of the number of new (trial) subscribers in March, 2000, or some other estimate of subscribers per month (adjusted as you see fit, since you're the forecaster), and enter it into the appropriate cell in the spreadsheet (cell G3). This is then multiplied by 12 to get the total new subscribers for the year 2000 (note that this is a simplification, since there may be seasonal patterns, as well as growth during the year).