KVL and sensitivity of a simple circuit

[adamaero]

Homework Statement

Homework Equations

The Attempt at a Solution

Note to self - simple diode concept: http://www.cs.tut.fi/kurssit/TLT-8016/Chapter3.pdf#page=5

Unsure about this KVL (above).

For the last sensitivity part, equations be falling out of the sky...

 

[Tom.G]

See if it helps with the schematic rotated 90 degrees like this.

If that doesn't quite do it,

Spoiler

mentally slide the batteries around to be on the left hand vertical.