1. The problem statement, all variables and given/known data In the attached image, I'm confused on how the first circuit reduces to the second circuit. 2. Relevant equations Is=Vs/R1 3. The attempt at a solution I know that in order to do a source transformation that I need to have a current source in parallel with a resistor or a voltage source in series with a resistor, but in the attached image that comes from my textbook's solution manual, I'm not exactly sure how they simplified the first circuit to the second. When I tried it, I thought that I could replace the 10 mA current source and 4 kohm resistor in parallel with a 40 V source and a 4 kohm resistor in series, and then the 4 kohm and 1 kohm resistors would be in series so they'd add up. But then, after I did that, I wasn't sure what to do with the 25 mA and how to simplify it to get it to look like that second circuit. Could someone please try to explain this? I'm taking an online class and my textbook doesn't have any complex examples like this for me to refer to. Thanks so much for your time!