They are looking for the resultant force acting on the body no the mass you didn't answer the question

The mass of the body is $m = 8\, \text{kg}$.
The uniform acceleration of the body is $a = 5\, \text{m/s}^2$.
We need to find the resultant force acting on the body, $F_{net}$.

Newton's Second Law states that the resultant force ($F_{net}$) acting on an object is equal to its mass ($m$) multiplied by its acceleration ($a$):

The resultant force acting on the body is $\text{40 N}$.