Hi! each question below has the answer (Bold). Could you please explain to 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. *c) 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 break-even point (in dollars) if fixed costs are $540,000 and variable cost are 70% of sales. a) $3,850,000 *b) $1,800,000 c) $1,650,000 d) $900,000