Yale has numerous athletic facilities, including the Yale Bowl (the nation's first natural "bowl" stadium, and prototype for such stadiums as the Los Angeles Memorial Coliseum and the Rose Bowl), located at The Walter Camp Field athletic complex, and the Payne Whitney Gymnasium, the second-largest indoor athletic complex in the world. October 21, 2000, marked the dedication of Yale's fourth new boathouse in 157 years of collegiate rowing. The Richard Gilder Boathouse is named to honor former Olympic rower Virginia Gilder '79 and her father Richard Gilder '54, who gave $4 million towards the $7.5 million project. Yale also maintains the Gales Ferry site where the heavyweight men's team trains for the Yale-Harvard Boat Race.

Answer this question, if possible (if impossible, reply "unanswerable"): How much did the Richard Gilder Boathouse cost to construct?
$7.5 million