IAS 23 Borrowing costs

Leclerc has borrowed $2.4 million to finance the building of a factory. Construction is expected to take two years. The loan was drawn down and incurred on 1 January 20×9 and work began on 1 March 20×9. $1 million of the loan was not utilized until 1 July 20×9 so leclerc was able to invest it until needed leclerc is paying 8% on the loan and can invest surplus funds at 6%. Calculate the borrowing costs to be captalised for the year ended 31 december 20×9 in respect of this project .
A) $130000
B) $192000
C) $100000
D) $162000
At the back of the kit the answer is
( A)

Borrowing costs march-December ($2.4m×8%×10/12) = $160000
Less investment income
($1m×6%×6/12) = ($30000)
____________
$130000
My question is why borrowing costs has been calculated from March 20×9 shouldn’t it be calculated from 1st January 20×9 as we took a loan on that date so we have to pay interest the date we took a loan no matter when the work started.