Harry runs a small street vendor service that contracts to produce and sell moulded plastic souvenirs $($key chains, commemorative plastic coins, plastic animals, etc.$)$ at small fairs. As owner of the firm, Harry must decide how much of each product to produce. What is a key element of this decision?

Question $1$Select one:

a$.$

how costs will vary as he changes the level of production

b$.$

the cost of bookkeeping services

c$.$

the fixed cost of production

d$.$

the cost of his selling booth

e$.$

None of the above.