5. a. The circuit below shows four identical bulbs connected to an ideal (resistance-less) battery. Rank the bulbs in order from brightest to dimmest. Use "=" to indicate the same brightness. Explain how the ranking was determined.
b. Write an equation that relates the voltage across bulbs 3, 5 and 6 to the battery voltage.
c. Bulb 1 is removed from its socket. Does the brightness of bulb 3 increase, decrease or remain the same? Explain your reasoning.