The Fastest Rower Ever is rowing his canoe upstream in a straight river. He rows for 40 miles when his hat falls off into the river. He continues to row upstream for 10 more minutes before he realizes his hat had fallen. He immediately turns around to retrieve his hat, at which point his other hat falls off into the river. He retrieves the first hat at his initial starting point, then turns around immediately and retrieves the second hat 30 miles upstream from his original starting point. How fast does the Fastest Rower Ever row in still water, in miles per minute?