Answer:
5 x n, where n is any natural number.
Step-by-step explanation:
If A is a 6 x 5 matrix, it means that A has 6 rows and 5 columns, this means that if a matrix B can be multiplied by A, then each one of its columns must have 5 entries. Therefore, B has to be a matrix with 5 rows and it might have any arbitrary number of columns, in other words B is a 5 x n matrix, where n must be a natural number bigger than 1.
