Question 1143887
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Since A is 5 x 3 matrix, the matrix {{{A^t}}} is 3 x 5 matrix (3 rows and 5 columns).


Since the matrix product  {{{A^t*B}}} is defined, it implies that matrix B has 5 rows.


Since the matrix C is 4 x 5 matrix and the matrix product BC is defined, it implies that matrix B has 4 columns.


<U>ANSWER</U>.  Matrix B has 5 rows and 4 columns, i.e. is 5 x 4 matrix.
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