Charlie's Chocolate Factory manufactures chocolate bars and ships them directly to wholesalers and retailers across the country. The company has two product lines: milk chocolate bars and chocolate covered almonds. Classify the following company's expenses if the cost object is a single product line $($either milk chocolate bars or chocolate covered almonds$).$

Salaries for milk chocolate bars production line workers

a$.$

Indirect period cost.

b$.$

Direct product cost.

c$.$

Indirect product cost.

d$.$

Direct period cost.