june 2014 exam adjusted trading profit and capital allowance

Quest1 : Why is it the Trading Profit working 1 had the full 3840 (jan13-april13) and then 8/12 of the 12060 (may13-apr14).

here basis period
tax year profit
2012-2013 1st jan2013 -5th april2013 2880 ie3840*3/4months
2013-2014 1 jan2013 -31st dec 2013 11880 (3840+8040)
2014-2015 1st may2013-30th april2014 12060

1 sep 2013 18000 8% and 30% calculating i get 432 . sir, could you help me to solve this problem i dont know from were to deduct 432 capital allowance and overlapping profit is deducted in final year right i saw example 2 illustrate i understood that, but still this is confusing