a)

 

 

 

 

 

 

 

 

 

 

b) If the voltage across the limiting resistor is 3.6 volts and the current is to be limited to 80mA (0.08A) then we can plug those values into Ohm's law and get an answer!!

V = I x R

R = V/I

= 3.6V/0.08A

=  45 ohms

note: resistors only come in certain sizes so you have to get the closest size

5% Standard Values
Decade multiples are available from 10 W through 22 MW
10 11 12 13 15 16 18 20 22 24 27 30
33 36 39 43 47 51 56 62 68 75 82 91