[单选题]
A roller coaster starts from re:hvjon wmim/5 pf;-4 wst 3lo( a. p+v8)ga zmecuat a point 45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at the top of the next slope, which is 30 m above the bottom of the l3(z)p vc8+gm. aoauedip?
