In your circuit toolbox, you only have a collection of resistors ( R1=100 Ω, R2=10 Ω, R3=60 Ω) and some switches that can be open or closed. Construct a circuit filling in all four boxes, such that the equivalent resistance between A and B is 15 Ω.

multiply 2kg by latent heat of vap

there are no contact forces mentioned on the list of choices that you've provided.

blue light is scattered in different directions by the tiny molecules of air. blue is scattered more than other colours because it has a shorter distance to travel which results in smaller waves. this is why we see a blue sky most of the time.