Perform matrix multiplication manually up to 3 × 3 matrices but not limited to square matrices.

Perform the matrix multiplication $\begin{pmatrix} 2 & 3 \\ 1 & -1 \end{pmatrix} \begin{pmatrix} 4 & 0 & 1 \\ 2 & 5 & -2 \end{pmatrix}$ and state the resulting matrix.

A bakery uses matrices to track sales. Matrix \( P \) represents the number of units sold of three products (muffins, cakes, slices) at two outlets, and matrix \( Q \) represents the unit price (in dollars) for each product. Given: \[ P = \begin{pmatrix} 20 & 12 & 15 \\ 18 & 10 & 20 \end{pmatrix} \quad \text{and} \quad Q = \begin{pmatrix} 4 \\ 25 \\ 6 \end{pmatrix} \] Determine the product \( PQ \).

A catering company supplies meals to three venues (X, Y and Z). The table shows the number of vegetarian, meat and dessert items ordered by each venue per week. Each vegetarian item costs $8 to prepare, each meat item costs $12 to prepare and each dessert costs $5 to prepare. Use matrix multiplication to calculate the total weekly cost for each venue.