A student constructs a hand warmer that becomes hot to the touch when activated. It is activated when a pouch filled with 100 mL of water bursts and combines with a solid substance in a dry bag, as in the model shown below. The student wants to continue using the same solid. However, he finds that the hot packs he constructs do not become warm enough, so he wants to modify his design. He conducts a test using the same solid but with different concentrations, as shown in the table below. Mass of Solid (g) Initial Temperature (°C) Final Temperature (°C) 20 20 51 30 20 63 40 20 73 50 20 86 60 20 96 After further research, he found that temperatures above 70°C are too hot for human touch. He wants the hot pack to be as warm as possible, but not too hot to touch. Based on the information given, how much of the substance should the student use to best modify his hot pack?
A.
25 g
B.
40 g
C.
35 g
D.
45 g