The spring force = kx = mg.
k is spring constant = 200 N/m
x is the spring elongation = 0.2 m
F = 200×0.2= 40 N
Now, F = mg wil be the weight of the object
Thus, weight is 40 N.
Thus, now we can also find the mass of object, m = F/g = 40 N/9.8
Because g is acceleration due to gravity = 9.8 m/sec ^2
m = 4.08 kg