A machine in a factory can assemble 234 units in 3 hours. Matt wants to write an equation to represent this situation. He says that the independent variable is the number of units assembled; the dependent variable is the number of hours, and the constant of proportionality is 78. What mistake did Matt make in finding the parts of the equation that represents this relationship?
A. He found the incorrect constant of proportionality.
B. He multiplied the constant of proportionality by the dependent variable.
C. He reversed the independent and dependent variables.
D. He multiplied the number of units by the number of hours instead of dividing.