Three identical copper blocks are arranged in a straight line so that Block X (90 °C) touches Block Z (70 °C) and Block Z touches Block Y (50 °C). Which of the following best describes the initial direction(s) of heat flow immediately after contact is made?
a) Heat flows only from Block X to Block Z; no heat flows between Blocks Z and Y at first.
b) Heat flows from both Blocks X and Y toward Block Z simultaneously.
c) Heat flows from Block X to Block Z and from Block Z to Block Y simultaneously.
d) Heat flows directly from Block X to both Blocks Y and Z at the same rate.