When the function f(x) = 4(2)x is changed to f(x) = 4(2)x − 13, what is the effect? a. there is no change to the graph because the exponential portion of the function remains the same. b. the x-intercept is 13 spaces higher. c. the y-intercept is 13 spaces lower. d. all input values are moved 13 spaces to the left.