What are the model constant and the slope coefficient of x1 when the dummy variable equals 1

Question:

What are the model constant and the slope coefficient of x1 when the dummy variable equals 1 in the following equations, where x1 is a continuous variable and x2 is a dummy variable with a value of 0 or 1?
a. y` = 4 + 9x1 + 1.78x2 + 3.09x1x2
b. y` = -3 + 7x1 + 4.15x2 + 2.51x1x2
c. y` = 10 + 5x1 + 3.67x2 + 3.98x1x2