Stamp collecting has become an increasingly popular-and expensive-hobby. One favorite method is to save plate blocks (usually four stamps with the printing plate numbering the margin) of each new stamp as it is issued by the post office. But with the rising postage rates and increased numbers of new stamps being issued, this collecting plan costs more each year. Stamps, however, may have been a good place to invest money over the last 10 years, as the demand for stamps previously issued has caused resale prices to increase 18% each year. Suppose a collector purchased $100 worth of stamps 10 years ago, and increased his purchases by $50 per year in each subsequent year. After 10 years of stamp collecting, what is the future worth of the stamp collection?