(a)The reading of the balance = Tension in the stringAnd tension in the string = 20g.So, the reading of the balance = 20g = 200 N(b) If the balance is heavy, the reading will not change because the weight of spring balance does not affect the tension in the string.(c) If the blocks have unequal masses, the spring balance will accelerate towards the heavy block with an acceleration a. Then the reading will be equal to the tension in the string.Suppose m1​>m2​.Then tension in the string, T=m1​+m2​2m1​m2​g​.