Answer: $94,000
Step-by-step explanation:

At 10,000 units;
total cost = $10,000 × 10
= $100,000
At 20,000 units,
Total cost = 20,000 × 6.5
= $130,000
Variable cost per unit using high low method:

= $3 per unit
Hence,
Total fixed costs = Total cost at 20,000 units - (No. of units × Variable cost per unit)
= $130,000 - (20,000 × 3)
= $70,000
Hence total cost at 8000 units = (No. of units × Variable cost per unit) + Total fixed costs
= (8000 × 3) + 70,000
= $94,000