How does a transformer affect the voltage and current?

$A$ thermal power plant produces electric power of $600 \ kW$ at $4000 \ V$,which is to be transported to a place $20 \ km$ away from the power plant for consumers' usage. It can be transported either directly with a cable of large current carrying capacity or by using a combination of step-up and step-down transformers at the two ends. The drawback of the direct transmission is the large energy dissipation. In the method using transformers,the dissipation is much smaller. In this method,a step-up transformer is used at the plant side so that the current is reduced to a smaller value. At the consumers' end,a step-down transformer is used to supply power to the consumers at the specified lower voltage. It is reasonable to assume that the power cable is purely resistive and the transformers are ideal with a power factor unity. All the currents and voltages mentioned are rms values.
$1.$ If the direct transmission method with a cable of resistance $0.4 \ \Omega \ km^{-1}$ is used,the power dissipation (in %) during transmission is:
$(A) 20$ $(B) 30$ $(C) 40$ $(D) 50$
$2.$ In the method using the transformers,assume that the ratio of the number of turns in the primary to that in the secondary in the step-up transformer is $1:10$. If the power to the consumers has to be supplied at $200 \ V$,the ratio of the number of turns in the primary to that in the secondary in the step-down transformer is:
$(A) 200:1$ $(B) 150:1$ $(C) 100:1$ $(D) 50:1$
Give the answer for question $1$ and $2$.

$A$ $60\, W$ load is connected to the secondary of a transformer whose primary draws line voltage. If a current of $0.54\, A$ flows in the load,what is the current in the primary coil? Comment on the type of transformer being used.

$A$ distribution transformer with an efficiency of $90 \%$ supplies power to a colony of $10$ homes. All the $10$ homes have an electrical oven running at the same time,each drawing $20 \ A$ current from $220 \ V$ lines. The power dissipated as heat in the transformer is: (in $kW$)

$A$ transformer with efficiency $80\%$ works at $4\, kW$ and $100\, V$. If the secondary voltage is $200\, V$, then the primary and secondary currents are respectively:

In a transformer,the primary has $500$ turns and the secondary has $50$ turns. If $100 \ V$ is applied to the primary coil,the voltage developed in the secondary will be.....$V$