On January 1, 2017, Plaid Corporation begins construction on a new warehouse. The construction project qualifies as a self-constructed asset. Plaid had the following expenditures on the project during 2017:

January 1, 2017 $200,000

July 1, 2017 $600,000

December 1, 2017 $120,000

What are the average accumulated expenditures used to calculate interest on the project in 2017?

a.) $510,000

b.) $420,000

c.) $310,000

d.) $460,000

I thought it was D, but it said I was wrong.