Answer : The mass of  required are, 35 kg
 required are, 35 kg
Explanation :
First we have to calculate the mass of  .
.
The first step balanced chemical reaction is:

Molar mass of  = 115 g/mole
 = 115 g/mole
Molar mass of  = 87 g/mole
 = 87 g/mole
Let the mass of  be, 'x' grams.
 be, 'x' grams.
From the balanced reaction, we conclude that
As,  of
 of  react to give
 react to give  of
 of 
So,  of
 of  react to give
 react to give  of
 of 
And as we are given that the yield produced from the first step is, 65 % that means,

The mass of  obtained = 0.4542x g
 obtained = 0.4542x g
Now we have to calculate the mass of  .
.
The second step balanced chemical reaction is:

Molar mass of  = 87 g/mole
 = 87 g/mole
Molar mass of  = 55 g/mole
 = 55 g/mole
From the balanced reaction, we conclude that
As,  of
 of  react to give
 react to give  of
 of 
So,  of
 of  react to give
 react to give  of
 of 
And as we are given that the yield produced from the second step is, 80 % that means,

The mass of  obtained = 0.2296x g
 obtained = 0.2296x g
The given mass of Mn = 8.0 kg = 8000 g     (1 kg = 1000 g)
So, 0.2296x = 8000
x = 34843.20 g = 34.84 kg = 35 kg
Therefore, the mass of  required are, 35 kg
 required are, 35 kg