My students� book says:
Subject verb agreement: Using Expressions of Quantity
With most expressions of quantity, the verb is determined by the noun (or pronoun) that follows OF.
Two-thirds of the money belongs to me.
Two-thirds of the coins belong to me.
Twenty percent of my income goes for rent.
Twenty percent of my earnings go for rent.
Also, in another section of the book it says:
Expressions of time, distance and money usually require a singular verb.
Five thousand miles is too far to travel.
So I am inclined to agree with cunliffe that the answer is was.