Which of the following is a result of shifting a circle with equation

(x - 1)2 + (y - 4)2 = 16

to the right 4 units?

a. the x-coordinate of the center of the circle increases by 4.
b. both the x- and y-coordinates of the center of the circle decrease by 4.
c. the y-coordinate of the center of the circle increases by 4.
d. both the x- and y-coordinates of the center of the circle increase by 4.