Samplr problem$-4$

A supply is offered on the basis of fixed charges of R$03$ per annum plus

$1$ Baiza per unit or alternatively, at the rate of $2$ Baiza per unit for the first $400$ units per annum and $1\mathrm{.}5$ Baiza per unit for all the additional units.

Find the number of units taken per annum for which the cost under the two tariffs becomes the same.

Sample probkem$-5$

An electric supply company having a maximum load of $50$ MW generates $18x10^7$ units per annum and the supply consumers have an aggregate demand of $75$ MW $.$ The annual expenses including capital charges are :

For fuel $=$ RO $18000$

Fixed charges concerning generation $=$ RO $5600$

Fixed charges concerning transmission $=$ R$06400$ and distribution

Assuming $90\%$ of the fuel cost is essential to running charges and the loss in transmission and distribution as $15\%$ of kWh generated,

Deduce a two$-$part tariff to find the actual cost of supply to the consumers.$($ for both i need to understand how i can solve with the solution $)$ Thanks