Paper 1 October/November 2017 Accounting (9706/11) A Level

A business marks up all of its products by 20% on total cost to calculate a selling price.
Each unit of product uses 4 hours of direct labour and 2 kilos of direct material.
The correct overhead absorption rate to be used is $8 per direct labour hour.
In error the book-keeper used a rate of $13 per direct labour hour.
What was the effect of this error on the selling price of one unit of the product?