b$)$ Two reservoirs are connected by two parallel pipelines with diameters of $0\mathrm{.}8m$ and $0\mathrm{.}6m.$ The pipelines are both $2\mathrm{.}6km$ long with a friction factor of $0\mathrm{.}2.$ The combined discharge through the pipelines must be at least $1\mathrm{.}7\frac{m^3}{s}.$

i$)$ When the total discharge is $1\mathrm{.}7\frac{m^3}{s},$ what is the flow rate in the individual pipelines?

ii$)$ If the larger pipeline has to be taken out of service for maintenance, what proportion of the total discharge will be lost?

iii$)$ What is the minimum difference in the elevation of the surface water level in the two reservoirs required to maintain a flow of $1\mathrm{.}7\frac{m^3}{s}$ through the pipelines?