How to pull a range of values and add it to a date depending on it meeting a certain condition

Am trying to automatically sum up Dates based on a certain size of a feature and it's estimate and I am wondering if we can do this without if statements?

So If I enter a new feature of a certain size among Low, Medium, High etc and enter one of these as an upcoming feature and give a start date, I want the rest of the dates to be populated automatically.

List of values:

      Low Medium High (Feature Sizes)

A. 5. 10. 20

B 12 12 12

C 0 5 15

Desired table: ( I just give details in column A, B, C and it fetches values in columns D & E based on the value in Column C)

I know I can do it with multiple ifs but I am wondering if there is a cleaner way of doing what I am currently doing.

Better to use ranges, but logic is like: =B6+INDEX({5,10,20;12,12,12;0,5,15},{1,2,3},XMATCH(C6,{"Low","Medium","High"}))