A mix of three materials into a process produces 0.9 litres of a finished product, with 10% loss of input in the process. Standard material costs are as follows per 0.9 litres of output. Material $ X 0.5 litres at $2 per litre 1.00 Y 0.4 litres at $1.50 per litre 0.60 Z 0.1 litres at $4 per litre 0.40 2.00 During a control period, 4,000 litres of output were produced. These used 2,810 litres of Material X; 1,910 litres of Material Y; and 380 litres of Material Z. What is the materials yield variance?