Read this and answer the question. If the question is unanswerable, say "unanswerable".

There are seven state parks within the confines of New York City, including Clay Pit Ponds State Park Preserve, a natural area which includes extensive riding trails, and Riverbank State Park, a 28-acre (110,000 m2) facility that rises 69 feet (21 m) over the Hudson River.

How many meters is Riverbank State Park elevated above the Hudson River?
21