The elevator car moves with acceleration a. The passenger in it drops the book. what is the acceleration of the book

The elevator car moves with acceleration a. The passenger in it drops the book. what is the acceleration of the book relative to the elevator if it moves up? a) a + g b) g-a c) a-g d) ag

Consider two objects: a book and an elevator floor.
These are two moving objects. The vectors of the speeds of the elevator and the book are directed in the same direction, which means that the speed of convergence of the floor of the elevator and the book is equal to the sum of the speeds of the elevator and the book.
Elevator acceleration formula:
a = (V – V0) / t.
In this case, the body immediately acquired acceleration, and at the initial moment of time it was at rest, therefore V0 = 0.
Then, a = V / t.
Book acceleration formula:
g = V1 / t.
The speed of convergence between the book and the floor of the elevator is:
Vc = V + V1 = a * t + g * t = t * (a + g).
This means that the acceleration of the book relative to the elevator is a + g.
Answer a).