Help with an object that uses a circles edges which are all tangent

So here is what I'm working with:

I'm having trouble properly creating the arc of DE. I tried making it tangent to the initial circle of the first arc AB, but I'm not getting the correct arc length.

Here us the file I'm working with:

HW 10 Cam arm.dwg

Have you seen this, I didn't watch the whole video so I don't know if it will be of any use

... but I'm not getting the correct arc length.

I do not see any arc length specified on the drawing?

What is R value?

I suspect you are withholding critical information needed to solve the problem. What book (title, edition, author, page) did this come from?

Assuming you have a-b drawn correctly, and the lines you have drawn are the points where each arc starts and stops, then immediately after creating arc a-b, start the arc command again, hit enter, pick point C, start arc, hit enter pick D, repeat...

You can draw an arc over the top of a-b picking a start point, a mid point on the existing arc, and the end point, and continue with the above.

One of the things in the diagram that may confuse is that each Arc has a different center pt location not the common one shown by the angles. I had a random go and to get correct arc with a rise is quite complicated not just increase previous radius by rise. There would be a mathmatical answer in the surveyors handbook.