Heat Is Added to a Substance at a Constant Rate

Heat is added to a substance at a constant rate. The substance starts as a solid and is melted; the liquid is heated and vaporized; finally, the vapor is heated. This process is shown in the graph. The latent heat of fusion can be found by

A) multiplying the length of B in seconds) by the rate at which heat is added, and dividing by the mass of the substance.
B) multiplying the length of D in seconds) by the rate at which heat is added, and dividing by the mass of the substance.
C) multiplying the slope of A by the rate at which heat is added, and dividing by the mass of the substance.
D) multiplying the slope of C by the rate at which heat is added, and dividing by the mass of the substance.
E) multiplying the slope of E by the rate at which heat is added, and dividing by the mass of the substance.