[单选题]
A roller coaster starts at ak /h u,+s4ee0mjuop) d point 30 m zqni2d4 (yt4zabove the bottom of a dip with a speed of 25 m/s (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at the top of the next slope, which is 45 m above the bz4q2( ynzt4id ottom of the dip?
