When dealing with complex systems, the creation of a product concept can be useful. Which of the following statements are true?

a) The product concept exclusively describes the greatest added value of the product
b) After the Product Backlog has been initially filled, one should summarise the
fundamental product aspects and characteristics in a concept
c) A product concept is only used in large and distributed projects
d) Initially, the product concept is formulated based on the product idea and before the Product Backlog is filled.