6. Using R as a calculator a) Use the $ notation shown in the video to write out the equations for the circumference and area of a circle. Remember that C = 2r and A = r. To get Greek letters to show in an equation, use \pi for example. To get a multiplication sign in the formula use \times. b) Write code to calculate the circumferences and areas of circles with radii of 0.5 and 2 cm. If you want, you can create a variable such as rad