NEC ECC: How is the total of the Prices calculated for Option D?

How is the total of the Prices calculated?

The total of the Prices is the total of:

	The quantity of work which the Contractor has completed for each item in the Bill of Quantities multiplied by the rate and

	A proportion of each lump sum which is the proportion of the work covered by the item which the Contractor has completed (see Clause 11.2(33)).