Can someone explain how we get the solutions please?

F 31 JAN Maddie sold hat the go Maddie is reaistered for VAT and makes standard-rated supplies only goods to Julie for 76 without charging any v without charging any VAT because Maddie believes die so were exempt from VAT. Maddie has now discovered that VAT should have been charged on this sale How much VAT is payable on this sale and by whom? The amount of VAT payable is A 12.67 B 15.20 The VAT is payable by C Maddie D Julie Lolda