Problem $4$: The two reservoirs are connected with a cast iron pipe. The total

length of the pipe is $15$ m $.$ For the first $10$ m $,$ from high level tank, the diameter

is $100$ mm and then diameter is suddenly enlarged to $200$ mm $.$ Calculate the flow

rate of water if the level of tank $1$ is $15$ m higher than tank $2.$ Consider all losses

and take value of coefficient of friction $f$ as $0\mathrm{.}02$ for all sections of pipe.