Final answer:
To create a matrix representing the cost of materials used by each person, use matrix multiplication. Multiply the row corresponding to Michael by the total number of items he made to get the cost of materials for the items Michael made.
Step-by-step explanation:
To create a matrix that represents the cost of materials used by each person, we can use matrix multiplication. Let's say we have a matrix M representing the amount of materials used by each person, and a matrix C representing the cost of each material. The matrix multiplication of M and C will give us a matrix R, where each element represents the total cost of materials used by each person. To find the cost of materials for the items that Michael made, we need to multiply the row corresponding to Michael in matrix R by the total number of items he made.