Matrix multiplication from scratch

You will write three functions: one that tells you whether two matrices can be multiplied, one that multiplies them by the row-by-column rule, and one that finds a power of a square matrix. A matrix is a list of rows. The checker tests many cases.

The idea. The product $AB$ exists when the number of columns of $A$ equals the number of rows of $B$. Entry $(i, j)$ of $AB$ is the sum of A[i][k] * B[k][j] over k. A power $A^n$ is $A$ multiplied by itself $n$ times.

Your tasks.

1. Finish can_multiply(A, B). Return True or False.
2. Finish multiply(A, B). Return the product as a list of rows.
3. Finish power(A, n). Return $A^n$ for $n \ge 1$, using multiply.