Tonto Rain Shields sells 3 types of umbrellas. Umbrella A sells for $20 and has variable cost of $9.00 per unit. Umbrella B sells for $17.00 and has variable cost of $12.00 per unit. Umbrella C sells for $9.00 and has variable costs of $6.00 per unit. The company sells in a mix of 2 units of A, 3 units of B, and 5 units of C. What is the weighted average contribution margin per unit for Tonto

The prebisch–singer hypothesis concludes that: a. technology lowers the cost of manufactured products, so developing countries should see an increase in their terms of trade. b. developing countries experience a long-run decline in their terms of trade, as the demand for primary products in higher-income countries declines relative to their demand for manufactured goods. c. because of unfair trading practices, labor in developing countries is exploited. d. opec has been responsible for a slowdown in the world's standard of living.