A substance has a triple point of -18.7 °C and 244 mmHg. What will happen to a solid sample of the substance if it is warmed from -29.2 °C to 0°C at a constant pressure of 203 mmHg?
a. The solid will melt into a liquid.
b. Nothing will happen, the solid will remain a solid.
c. The solid will sublime into a gas.