I need to put 24 photos on a 20x16 paper.?

The mat is 1 1/8 inch off the edges all around and there needs to be 1/4 inch in between each photo. This doesnt include the outer edge of the outer photos. There are 6 photos horizontally and 4 photos verticaly.(4 rows of 6) Please help me out this has been a real brain teaser.