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Barnes Company reports the following for its product for its first year of operations.

Direct materials $$33$ per unit

Direct labor $$23$ per unit

Variable overhead $$10$ per unit

Fixed overhead $$78,000$ per year

Variable selling and administrative expenses $$3$ per unit

Fixed selling and administrative expenses

$$35,000$ per year

The company sells its product for $$130$ per unit. Compute contribution margin using variable costing assuming the company

$($a$)$ produces and sells $3,000$ units and

$($b$)$ produces $3,900$ units and sells $3,000$ units.