Well, let's see, f prime of x is equal to 2x minus 6. And so we need to figure out at what x value, especially it has to be within this open interval, at what x value is it equal to 1? So this needs to be equal to 1. So let's add 6 to both sides. You get 2x is equal to 7. x is equal to 7 halves, which is the same thing as 3 and a half. So it's definitely in this interval right over here. So we've just found our c. c is equal to 7 halves.