Microeconomics questions pls help?

Question

If a perfectly competitive firm sells 30 units of output at a price of $10 per unit, its marginal revenue is ______.

$10

more than $10

less than $10

$300

Marginal revenue is a firm's ______.

ratio of profit to quantity

ratio of average revenue to quantity

price per unit times the number of units sold

increase in total revenue when it sells an additional unit of output

For a firm producing at any level of output less than the most profitable one, an increase in output adds ______.

more to total cost than to total revenue

more to total revenue than to total cost

the same amount to total revenue as to total cost

to total revenue but not to total cost

In the short run, a perfectly competitive firm produces output and earns zero economic profit if _____.

P > ATC

P = ATC

P < AVC

AVC > P > ATC

Answer 1

the first answerer is correct...........

Answer 2

1) MR=$10

2) increase in total revenue when it sells an additional unit of output

3) more to total revenue than to total cost

4) P = ATC

P.S. thanks for support Chris ;)