EFG Co$.$ purchases and resells T$-$shirts. On April $1,2019,$ the company purchased ten T$-$shirts for $$7$ each and sells them all for $$10$ each. What is the cost of goods sold on the sale?

Select one:

a$.$ $$100$

b$.$ $$70$

c$.$ $$30$

d$.$ None of the choices available