Tangible NCA – Borrowing Costs (Qn in BPP)

Dear Chris,

I have difficulty understanding a question in BPP Kit – Tangible NCA:

Leclerc Co has borrowed $2.4 million to finance the building of a factory. Construction is expected to take two years. The loan was drawn down on 1 January 20X9 and work began on 1 March 20X9. $1 million of the loan was not utilised until 1 July 20X9 so Leclerc was able to invest it until needed.
Leclerc Co is paying 8% on the loan and can invest surplus funds at 6%.
Calculate the borrowing costs to be capitalised for the year ended 31 December 20X9 in respect of this project.

Borrowing costs (March – December) : $2.4m × 8% × 10 / 12 = 160,000
Investment income: $1m × 6% × 4/12 = 20,000
Ans: 140,000

The part that I do not understand is that – why do they only account 4 months of investment income? Since the question stated “$1 million of the loan was not utilised until 1 July 20X9 so Leclerc was able to invest it until needed”, I thought that the investment is from 1 Jul – 31 Dec (6 months)? Or did I misinterpret the question?

Thank you for your time! Hope to hear from you soon.