General ACCADeposit/Deferred Income question

Hi I'm not sure if this is the right place to post this question from an audit test... We are acting as agent for a client which tasks us with managing their publicity account. They have an annual spend of £240,000 which started in Jan 2015 for 12 insertions, one per month on an equal basis. We have received the following payments from the client: 1 Jan 15, 20% deposit on account - no invoice raised 1 Apr 15, 30% of total spend on account - no invoice raised The only sales invoice raised in the year was 31 Mar 15 for £30,000 What balance would appear in the sales ledger & any provisions relating to income as at: 31 Jan 15 28 Feb 15 31 Mar 15 30 Apr 15 Does anyone know the answer? Thanks