Show work please!

A firm is about to undertake the manufacturing of a product, and is weighing three capacity alternatives: small job shop, large job shop, and repetitive manufacturing plant. The small job shop has fixed costs of $4,000 per month, and variable costs of $12 per unit. The larger job shop has fixed costs of $12,000 per month and variable costs of $6 per unit. The repetitive manufacturing plant has fixed costs of $19,000 and variable costs of $2.5 per unit.

a) Identify the demand ranges where each capacity choice should the firm make.

b) Which alternative should the firm choose if the demand for the product is expected to be 1,900 units per month?