Urgent Help Needed to provide Quantity Discount for Photo Print Sizes!

[Jules4Love]

Hi,

I need urgent support for Easy Populate Standard or a solution that will permit me to apply quantity discount to multiple products at once . I am currently setting up a shop front for a Printing company using Zen cart. The company have four main print sizes. Each Print Sizes will have 1000+ products with quantity discount.
I need to find a way of creating bulk quantity discount for each of these print sizes.

The first print size retails at $7.50 for the first print and 50 cents for each additional prints. An easy calculation of $7.50 + (Quantity * 0.5).

The second print size retails at $10 for the first print and $2 for each additional prints.
The third print size retails at $12.50 for the first print and $4 for each additional prints.
The fourth print size retails at $12.50 for the first print and $5 for each additional prints.

I have investigated how I could configure categories with specific quantity discount but this has not worked. I am hoping to get advice about how I can modify PHP codes if necessary or use Easy Populate to achieve this.

Thank you in advance
Jules