Anya buys 4 shirts and 3 hats. She pays $100 and receives $21.50 in change. Each shirt costs the same amount. Each hat costs $13.50. Work out the cost of one shirt.

1. (a)Anya buys 4 shirts and 3 hats. She pays $100 and receives $21.50 in change. Each shirt costs the same amount. Each hat costs $13.50. Work out the cost of one shirt.[3]
2. (b)The exchange rate between dollars ($) and euros (€) is $1 = €0.91 . Anya buys a new camera for $150. She sees the same camera for sale online for €140. Calculate the difference between the price in dollars and the price in euros. Give your answer in dollars, correct to the nearest cent.[2]
3. (c)Anya invests $600 in a savings account. The account pays compound interest at a rate of r% per year. At the end of 3 years the total interest is $21.86. Calculate the value of r.[3]