Give a mathematical example of a double trade discount, whereby the original price is $$200\mathrm{.}00$ and it is discounted by $20\%$ if you pay $10$ units, and then it is discounted and additional $10\%$ if you buy $20$ units. $($This requires two calculations$).$

How much will you buy $10$ units?

What is the average price for $1$ unit under the first scenario?

How much will you pay for the $20$ units?

What is the average price for $20$ unit?