Q$\mathrm{.}2)$ Given that the pipe in Fig $($a$)$ is $300$ m long, that water is initially flowing through it at $0\mathrm{.}8\frac{m}{s},$ and that pressure waves travel along it at $1000\frac{m}{s},$ find the maximum water hammer pressure at the valve, and at points $100$ m and $200$ m from the valve, $(a)$ if the valve is completely closed instantaneously, and $(b)$ if the valve is partially closed instantaneously, reducing the flow velocity to $0\mathrm{.}2\frac{m}{s}.$