A circular field with inner radius of 10 meters and outer radius of 20 meters is divided into 5 successive stages for ploughing, The ploughing at each stage, with starting points P1, P2, P3, P4 and P5, was allotted to one of the five farmers F1, F2, F3, F4 and F5, not necessarily in that order. <br />F5 was allotted the stage starting at point P4.<br />The stage from P5 to P3 was not the first Stage.<br />F4 was allotted the work of the fourth stage.<br />Finishing point of stage 3 was P1 and the work was not allotted to F1.<br />F3 was allotted the work of the stage ending at point P5<br /> What are the starting and ending points of the field ploughed by F4?