Imagine you own a building firm and you have quoted a customer £100,000 to build a large extension on their home. You estimate that the job will cost you £80,000 so that you will make an estimated...

Imagine you own a building firm and you have quoted a customer £100,000 to build a large extension on their home. You estimate that the job will cost you £80,000 so that you will make an estimated profit of £20,000. However, if you have underestimated your costs by 10% how will this affect your profit? How much will your profit be reduced by in pounds and in per cent?