Answer:
5 seconds
Step-by-step explanation:
Acceleration,

Where v and u are the final and initial velocities of the roller coaster respectively, t is the time taken for the coaster to reach the top of the hill.
Making t the subject then

Substituting -3 m/s2 for a since it decelerates, 25 m/s for u, then 10 m/s for v then
