Hi! each question below has answer (Bold). Could you please explain me why those are the answers and why the others (each) are wrong? I am preparing for my final and just want to make sure I really understand why and why not of each of them. Thanks.

4) Which of the following is true of a variable cost? a] Total variable cost remains constant with changes in the number of goods sold. b] Unit variable cost decreases with an increase in production. *0] Unit variable cost remains constant with changes in production. d] Total variable cost decreases with an increase in the number of goods sold. 5) Compute the breakeven point {in dollars} if fixed costs are $540,000 and variable cost are 70% of sales. a] $3,850,000 *0.) $1,300,000 0] $1,650,000 0] $900,000