Answer:
Alright so here's the catch. Zig knows he went to bed at 10pm , but his calculations show 12pm. So basically,that could mean that his lights went off at 12pm , bc he makes his calculations according to the light bulb (lol , thats why its mentioned in the question). So theres a two hour difference.
Watt is the unit of power , so theyre asking us to find the power of the new bulb.
power= work done by time.
time= 2hrs
Power=75watts.
we need work done , so work done = power * time = 75*2=150 joules.
but , new bulb works two hours more than previous one , so time taken = 4 hours , work done=150 joules.
therefore power= work done/time= 150/4=37.2 watts.