A firm has two inputs: X and Y. The firm understands these inputs to be substitutable. The firm's standard mix is 2 unit(s) of input X for every 12 unit(s) of input B.

• Input X costs $25 per unit
• Input Y costs $6 per unit

The firm's actually used 4,000 total input units, with 1,000 units of input X and 3,000 units of input Y.

What is the firm's mix variance for these inputs?

Please show work