For this example, I am using Image A:
-4000 x 6000 pixel dimension at 300 pixels per inch.
-The aspect ratio is 2:3 (1.5)
-Available print sizes for this image which will provide a full frame crop are as follows: 4x6, 6x9, 8x12, 10x15, 12x18, 16x24, 20x30, 24x36.
Oh yeah, make sure to have the Pixel Chart on hand as well. As we look at the required pixel dimensions on the Pixel Chart we can see Image A will be able to print up to 20x30 (would print at 200 dots per inch). I would most likely opt to print at 16x24 and obtain the higher print resolution of 250 dots per inch.