So we just have to pick kind of another placeholder variable that doesn't have to be t. It could be alpha, it could be gamma, it could be a, b, or c, whatever we choose. But this is still right over here. This is a function of x. But when you take the derivative of both sides, you realize that the function f, which is graphed here, and if this were the x-axis, then this would be f of x. If this is the t-axis, then this is y is equal to f of t. But generally, this is the graph of our function f, which you could also view as the graph of g prime. If this is x, this would be g prime of x. And so we're thinking about the interval from, the open interval from five to 10, and we have g's derivative graphed here, and we wanna know a calculus-based justification from this graph that lets us know that g is concave up.