Please help me on this with a full explanation

a = 5 [m/s²]

Explanation:

We must perform a sum of forces on both axes (vertical axis and horizontal axis).

We see that the forces on the vertical axis are the same but in the opposite direction. In this way, there is no movement on the vertical axis y. and we can find the mass of the body.

∑Fy = 0

Fnorm - Fgrav = 0

We know that the force of gravity is equal to the product of mass by gravitational acceleration.

where:

m = mass [kg]

g = gravity acceleration = 10 [m/s²]

Since there is only one force on the horizontal axis, this force generates accelerated motion. This force is equal to the product of mass by acceleration, as stipulated by Newton's second law.

∑F = m*a

where:

F = force = 50 [N]

a = acceleration of the body [m/s²]

i think the answer is b