Calculating current through a resistor
Partial solution to lead OP's thinking.

Figure 1. Original circuit layout.



simulate this circuit &ndash; Schematic created using CircuitLab
Figure 2. Exactly the same circuit but with more obvious parallel components R2 and R3.

Figure 3. Why is this not correct?
Figure 3 can't be correct because it shows &quot;R2 || R3&quot; in series with R4. Figure 1 clearly shows that R4 is connected in parallel with the current source so Figure 3 is incorrect.