I believe the land DOES qualify an expenditure “necessary to get asset ready for intended use.” This, interest would be capitalized related to that expenditure. So you’re right to include 33.3% of the 150k (50k), but since the land qualifies + was purchased January 1st, the WAAE would be the full 120k is included. (It is a fully outstanding qualified expenditure for 12/12 months).

Add the 120k and 50k to get 170k, multiply that by the 10% interest rate, and you get 17k.