The correct answer is: A. Gross margin percentage.
The constant gross margin percentage NRV method is a method of allocating joint costs to joint products based on the relative net realizable values of the products at the split-off point. The first step in this method is to calculate the net realizable value of each product. The second step is to calculate the gross margin percentage for each product. The third step is to allocate the joint costs to each product based on the gross margin percentage of each product.
The cost of split-off point is not used in the constant gross margin percentage NRV method. The cost of split-off point is the cost of processing the joint products beyond the split-off point. This cost is not relevant to the allocation of joint costs because it is incurred after the joint products have been identified.
The total production cost of each product is not used in the constant gross margin percentage NRV method. The total production cost of each product includes the joint costs and the costs incurred after the split-off point. This cost is not relevant to the allocation of joint costs because it includes costs that are not incurred until after the joint products have been identified.
The gross margin percentage is the percentage of sales revenue that remains after deducting the cost of goods sold. The gross margin percentage is used to allocate joint costs to joint products because it is a measure of the profitability of each product. The higher the gross margin percentage, the more profitable the product is.
Therefore, the third step in the constant gross margin percentage NRV method is to compute the gross margin percentage for each product.