4G ad 70% 09:16 Thandi Mandla Pty Ltd has the following total costs at two activity levels. At activity level (units) of 30 000, the total cost is N$760 000. At activity level (units) of 48 000, the total cost is N$940 000. Variable cost per unit is constant in this activity range, but there is an increase of N$ 18 000 in the total fixed costs when the activity exceeds 40 000 units. What are the total costs at an activity level of 36 000 units? a. N$825 000 b. N$815 000 c. N$814 000 O d. N$850 000