1. A careful analysis by Xhosa (Pty) Ltd cost accountant has determined that; if a plane operates for 1 450 kilometres (km) during a month, the average semi-variable operating costs is R1.50 per km. If a plane operates only 980 km during a month, the average semi-variable operating costs is R1.95 per km. Using the high-low method, the variable costs per km is calculated as: (Round to two decimal places): a. R0.56. b. R549. c. R1 911. d. R1 362