What do you mean by margin of safety? What does it indicate?

ABC Seating, a manufacture of chairs, had the following information for 2020 :

Sales - 2,400 units

Sales price - Tk. 40 per unit (Taka forty)

Variable costs - Tk. 15 per unit

Fixed costs - Tk. 19,500

Calculate :

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