(Solved): Consider a container of the shape obtained by revolving a segment of the parabola x=1+y^(2) around ...

Consider a container of the shape obtained by revolving a segment of the parabola x=1+y^(2) around the y-axis as shown below. The container is initially empty. Water is poured at a constant rate of 1c(m^(3))/(s) into the container. Let h(t) be the height of water inside the container at time t. Find the time t when the rate of change of h(t) is Maximum. I can't understand the solution of Chegg, mainly differentiating and functions formation part.