Interpreting the cumulative gains curve

You built a model to predict which donors are most likely to react on a campaign and built a cumulative gains curve plotted below. Assume you have budget to send a letter to the top 30 000 donors among the 100 000 donors. How many targets (donors that react) will you have reached, if there are 5 000 targets among the 100 000 donors? Recall that the cumulative gains curve shows for each value x on the horizontal axis the percentage targets that is reached when using the model.