There are two separate bags of coffee available at my local supermarket. Coffee Bag A is 200g and priced at £2.40. I need to use 15g of this coffee to get my desired coffee strength each day. Coffee Bag B is 500g and priced at £4.00. I need to use double the amount I used in Coffee Bag A to get my desired coffee strength each day. I will buy enough coffee to last me 30 days. Any excess coffee I will throw away at the end of the 30 days.