Describe the ways to change the internal energy in the following cases: a) primitive man produces fire by friction;

Describe the ways to change the internal energy in the following cases:
a) primitive man produces fire by friction;
b) water is heated in a pot on a fire;
c) the head of the match ignites when rubbing against the boxes;
d) an artificial satellite of the Earth heats up when entering the lower atmosphere;
e) the roof of the house is heated by sunlight.

a) work, b) heat transfer, c) work, d) work e) heat transfer.