Write three functions (1) rectangleArea (2) circleArea, and (3) triangleArea to compute and return the area of a rectangle, circle, and triangle, respectively. Use these functions in a program in which program will compute and print the area of (a) rectangle if user will enter'R' or 'r (b) circle if user will enter'd" ore: (c) triangle if user will enter Tor; The program will discontinue (stop) if user will enter E'or e