In the following figure, what is the value of the potential at points a and b?

Express your answer using two significant figures.

*Please explain each step and why each step takes place. Thanks in advance.

Answer:

drawing requires a sign in.

update: Assuming you want voltage with respect to ground.

point a is +5V

Current in loop is CW and is equal to (15–5)v / (4+1)Ω = 10/5 = 2 amps

voltage drop across 1Ω resistor is E = IR = 2 volts

so Vb = –2v

edit: to elaborate a bit on that last number:

start at ground and go CW around the loop. Voltage at point a is –2 volts

next point is –2+15 = +13.

next point is –2+12–8 = +5v

next point is back to ground, 0v.