short-circuit
In theory, the voltage across a wire is zero, so any components bypassed by a short circuit can be ignored when analyzing the circuit.
A real wire, however, is not an ideal conductor. Is there any real-world situation where you would have a circuit where a component is deliberately short-circuited?
First : Of course current flows through R3 and/or R5. They - and nothing else - connect to one end of a current source. As it is sourcing current, it must flow somewhere, and that means either R3 or R5 or both.
Second : Re-draw the circuit with nodes 1 and 2 shorted. Can you see that R1 and R4 are now in parallel? The same is true of R3 and R5. That lets you draw a much simpler circuit. You can now work out the voltage between node 3 and node 1/2 - ditto node 4.
At which point you know the voltage across every resistor, therefore the current through each. (Check your math : the R1 and R4 currents must sum to 20mA, ditto R3 and R5).
And having computed these, you can probably see how to calculate the answer to your question.
Best Answer
I worked with a guy who liked to do this:
simulate this circuit – Schematic created using CircuitLab
In normal operation the LED is short circuited. If the fuse blows you've got a nice indicator to tell you why your circuit suddenly stopped working.
I can't say I'm 100% sure of the wisdom of continuing to run current through the load once it's had a fault that makes it blow a fuse though.