Factoring costs and benefits

In ques 2 "H finance" of BPP book at the back in section C... This ques is asking for whether to take the servifes of factor or not. There is an information given in the question which is % accounts receivable of 90+ days of revenue = 2.5 in 2010 And this info is nowhere used in the solution. Can you explain what this means. There is also this other info of - " % of receivables at the year end " which is used to calculate cost of financing receivables in the solution. But what does that previously mentioned info means. Thanks