Answer:
a = 8.4 m / s²
Explanation:
The mean acceleration is defined by
a = (v_f- v₀) / (t_f - t₀)
where v are the final and initial velocities, respectively and t is the time interval
Let's apply this equation to our case
the final velocity is 99 m / s and the initial velocity is 57 m / s
a = (99 - 57) / (15 - 10)
a = 8.4 m / s²