What are the purposes of maintaining working capital?

XYZ enterprise had the following information for 2020 :

Sales 4,800 units
Sales Price (Per unit) Taka 80
Variable Costs (Per unit) Taka 30
Fixed Costs Taka 39,000

You are requested to Calculate :

(i) What is the Contribution Margin and Contribution Margin Ratio?
(ii) What is the break-even point in sales?
(iii) What is the margin of safety in units and sales?
(iv) If the company wishes to increase its contribution margin by 40% in 2021, by how much will it need to increase its sales if all other factors remain constant?