user: I'm working on a data analysis project where I need to multiply two matrices as part of my computations. The first matrix I need to work with is [[1, 2], [3, 4]], and the second one is [[5, 6], [7, 8]]. I need to calculate the product of these two matrices to proceed with my analysis. Can you help me with this calculation?

Available functions:
name: mat_mul
description: Multiplies two matrices.
parameters: type: dict
properties: matA: type: array
description: The first matrix.
items: type: array
items: type: integer
matB: type: array
description: The second matrix.
items: type: array
items: type: integer
required: matA
matB
name: calculate_mean
description: Calculates the mean of a list of numbers.
parameters: type: dict
properties: numbers: type: array
items: type: float
description: The list of numbers.
required: numbers