And then over here in blue, this is going to be plus 100 minus x squared over 16. Now let's take the derivative of this. So a prime, our combined area, the derivative of our combined area as a function of x, is going to be equal to, well, the derivative of this with respect to x is just going to be square root of 3x over 18. The derivative of this with respect to x was the derivative of something squared over 16 with respect to that something. So that's going to be that something to the first power times 2 over 16, which is just over 8. And then times, we're just doing the chain rule, times the derivative of the something with respect to x. The derivative of 100 minus x with respect to x is just negative 1.