40 dollars is the setup so it happens only once. It is a fixed cost.
10 dollars is for each shirt so it is a variable cost. Happens for every shirt.
Y is total cost:
Y= 40 + 10x
For one shirt:
Y=40+10(1)
Y=50
For five shirts:
Y=40+10(5)
Y= 90
For ten shirts:
Y=40+10(10)
Y=140
For fifty shirts:
Y=40+10(50)
Y= 540
