Use $"$if$"$ and "elif" statements only.

Oil & Gas Station Scenario

A gas station wants to write a program which is able to:

Display the following menu:

G: Gas

O: Oil

Allow the user to select one of the above options. The user can type $($ g or G $)$ and $($o or O $).$

If the user selects invalid option $($not $g/$G or o$/$O$),$ the program should display an error

message, as shown in Test $1.$

Calculate the cost of their oil and gas purchases from their wholesaler, including any

discounts and GST$.$ Calculation is based on the following business rules:

Oil must be purchased by the case. There are $12$ litres$/$case$.$

Oil costs the station $$1\mathrm{.}25$ per litre before discounts.

If the station purchases more than $6$ cases, they receive a $10\%$ discount off the

per litre price of the purchase.

Gasoline is purchased by the litre at a cost of $$1\mathrm{.}05$ per litre.

If the station purchases more than $2000$ litres, they receive a $10\%$ discount off

the per litre price.

Calculate GST according to the following table:

The user can type the province in lower$-$or upper$-$case letters.