5.100 How add a new row to bottom of matrix?

Given matrix

\[ \left [\begin {array}{cc}1 & 1 \\2 & 3 \\4 & 5 \end {array}\right ] \]

How to add row

\[ [a, b] \]

to end of the matrix?

restart; 
A:=Matrix([[1,1],[2,3],[4,5]]); 
the_row:=convert([a,b],Vector['row']); 
ArrayTools:-Concatenate(1,A,the_row);
 

\[ \left [\begin {array}{cc}1 & 1 \\2 & 3 \\4 & 5 \\a & b \end {array}\right ] \]