Yield Variance Question

Hi Sir

I am getting confused in the question below, can you please help me solve it

A chemical flavouring, product C is made by mixing two materials together:

Standard – Kg per batch – $ per kg – $ per batch

L – 300 – $1.30 – 390
H – 500 – $2.82 – 1,410

Input per batch 800kg

10% standard loss 80kg

Output per batch 720kg

For batch 1247 input as 250.5kg of L and 669.5kg of H. Output from the batch was 810kg of product C.

What is the yield variance?

I am getting confused with the 10% loss part.

Thank you in advance!
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