Answer:
a) The net force acting on the dog = 549 N
b) The acceleration of the elevator = 20 m/s²
Step-by-step explanation:
The mass of the dog, m = 25.0 kg
Force applied to the dog, F = 500 N
Acceleration due to gravity, g = 9.8 m/s²
A) The net force acting on the dog in the elevator is:

B) Calculate the acceleration of the elevator
F = ma
500 = 25a
a = 500/25
a = 20 m/s²