<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def multiply(a, col):
 """Multiply a matrix by one column."""

    a = a.reshape(4, 4, 4)
    col = col.reshape(4, 8)
    return fcat(
        rowxcol(a[0], col),
        rowxcol(a[1], col),
        rowxcol(a[2], col),
        rowxcol(a[3], col),
    )