Straight-Line Depreciation with Full-Year Policy Steps:

• Calculate annual depreciation for first vehicle: 20% × $20,000 =$4,000.
• Calculate annual depreciation for second vehicle: 20% × $10,000 =$2,000.
• Apply full-year depreciation to first vehicle for 2020: $4,000.
• Apply full-year depreciation to second vehicle for 2020 (per policy): $2,000.
• Total depreciation: $4,000 +$2,000 = $6,000.

Why D is correct:

• Straight-line at 20% yields fixed annual amounts per asset; full-year rule in purchase year ensures $2,000 for the second vehicle despite June purchase.

Why the others are wrong:

• A: Ignores first vehicle's $4,000 depreciation.
• B: Ignores second vehicle's $2,000 depreciation.
• C: Applies half-year convention to second vehicle ($1,000) + first's$4,000, violating full-year policy.

Final answer: D