Yield variance

Dear Tutor,
I have a question regarding the material yield variance. The question is from the BPP Kit

A mix of three materials into a process produces one litre of a finished product, with some loss of input in the process. Standard material costs are as follows per litre of output.

Material $
X 0.3 litres at $2 per litre 0.60
Y 0.6 litres at $3 per litre 1.80
Z 0.3 litres at $1 per litre 0.30
2.70
During a control period, 5,000 litres of output were produced. These used 1,400 litres of Material X; 3,100
litres of Material Y; and 1,250 litres of Material Z.

What is the materials yield variance?
A $412.50 (A)
B $150 (F)
C $469 (F)
D $562.50 (F)

Solution:
5,750 litres of input should produce (× 100/120) 4,791.67
They did produce 5,000.00
Yield variance in litres of output 208.33 (F)
Standard material cost per litre of output $2.70
Yield variance in $ $562.50 (F)

Could you please help me how to calculate the loss (100/120).
Thank you.