Howard, a Trustee, Bought a Brand New Car Costing £20,000

Howard, a trustee, bought a brand new car costing £20,000. He paid the deposit of £5,000 in January using his credit card. He paid this credit card debt in full using his own money. He paid the balance of £15,000 in March, again using his credit card, which at the time had a debit balance of £6,000. In April Howard repaid the whole of the credit card debt of £21,000 using money wrongly withdrawn from the trust.
Which of the following statements most accurately describes the rights of the beneficiaries?

A) The beneficiaries can assert a proprietary claim to the car because it cost less than the sum which was wrongly taken from the trust.
B) The beneficiaries cannot assert any proprietary claim to the car because it was purchased using a credit card and the trust money was used merely to pay a debt.
C) The beneficiaries can assert a proprietary claim to three-quarters of the value of the car because their funds were used indirectly to make this proportion of the purchase.
D) The beneficiaries can assert a proprietary claim to the whole value of the car because their funds were used indirectly to fund the whole of the purchase.