Percentage atom economy help! + pos rep

Completely forgotten how to do this, could someone explain pls and also write down the percentage a economy formula cos I kinda forgot it positive rep WILL be given!!!

In the past 150 years, three different processes have been used to extract bromine from potassium bromide. These processes are illustrated below.

Extraction Process 1
2KBr + MnO2 + 2H2SO4 → MnSO4 + K2SO4 + 2H2O + Br2

Extraction Process 2

The reaction of solid potassium bromide with concentrated sulfuric acid.

Extraction Process 3

The reaction of aqueous potassium bromide with chlorine gas.

Write an equation for Extraction Process 2 and an equation for Extraction Process 3. Calculate the percentage atom economy for the extraction of bromine from potassium bromide by Extraction Process 3. Suggest why Extraction Process 3 is the method in large-scale use today.

I presume you know how to write out the balanced equations.

Percentage atom economy is given by:

$\dfrac{\mathrm{Mass\ of \ desired \ product}}{\mathrm{Total \ mass \ of \ reactants}} \times 100$

Use the Ar and Mr values in the equation.

Thanks! Also how would you write out the equation for process 2?

There are a few possible answers for this question, I think. The products formed could be:

KHSO₄ or K₂SO₄
Br₂
SO₂
H₂O

See if you can write a balanced equation now.