Answer:(a) 50 N
(b)38.34 N
Explanation:
Given
Maximum tension(T) in line 50 N
(a)If line is moving up with constant velocity i.e. there is no acceleration
This will happen when Tension is equal to weight of Fish
T-mg=0
T=mg
Maximum weight in this case will be 50 N
(b)acceleration of magnitude 
T-mg=ma


m=3.91
Therefore weight is 
Let k be the spring constant. Then you have
188=k*21.8
k=188/21.8=8.62,
In the second part you use
m g= k x
x=m g/k= 38/8.62=4.4cm
4.4 cm is the answer