Lesson Sketch: mathematics of a cake sale

Intro:

There is a cake sale coming up and you plan to sell these flapjacks:

How much should you charge for one? Why? Will that make me a profit? How do you know? How much profit would I make? How could I work it out?

Main:

Give pupils the recipe: http://allrecipes.co.uk/recipe/3846/apricot-oat-flapjacks.aspx and either a table of prices or access to a supermarket website, such as http://www.tesco.com/
Pupils work out how much it costs to make a batch of 8 flapjacks and the profit they could make on each one sold.

Extension:

What are the most expensive parts of these flapjacks? Try to replace some things in the recipe with something similar in order to make the total cost lower. How much profit would you make now? How cheap could you make them?
Can you find a different cake recipe that would be cheaper to make?

Further Discussions:

This cake is slightly cheaper to make than the flapjacks:

Should I make these instead of the flapjacks? Why? Why not? What other considerations should I be making apart from price? (Time, effort, equipment needed, etc.)

You may discuss how some people factor time as money using a basic wage.