Help to fill and calculate number of circle in rectangle

I dont know how to start .I atached one picture:Date are :circle diam ,length and height.The circles should fill rectangle in honeycomb structure.

Thanks a lot
Untitled.pdf (71.2 KB)

start with researching circle packing and known algorithms for it.
If you are lucky there will be a good implementation in R or python , or some other language that you can learn to use, if not you may have to take a similar enough approach, and modify it for your needs.