A shop has the following operational data:

Product selling price per unit $=$ IDR $100$ thousand

Purchase cost per unit $=$ IDR $60$ thousand

Total fixed costs $=$ IDR $1$ million

How much is the Margin of Safety in rupiah if the shop targets sales of $40$ units?

a$.$ IDR $800,000$

b$.$ IDR $1,100,000$

c$.$ IDR $1,400,000$

d$.$ IDR $1,500,000$