Average variable cost is the total cost divided by quantity. Like this equation : TC(Q)/Q=Average Variable Cost.

Marginal cost is the 1st derivative of the total cost with respect to Q. So, if for instance, you have total cost = to 1+2x+4x^2, then marginal cost is = 2+8x, it is the cost for the last unit produced.

Marginal revenue is the revenue for the last item sold. If you have an equation for it, I would say that it is the same equation as marginal cost, otherwise in a perfectly competitive market, it should be constant.

Good luck.

Marginal cost is the 1st derivative of the total cost with respect to Q. So, if for instance, you have total cost = to 1+2x+4x^2, then marginal cost is = 2+8x, it is the cost for the last unit produced.

Marginal revenue is the revenue for the last item sold. If you have an equation for it, I would say that it is the same equation as marginal cost, otherwise in a perfectly competitive market, it should be constant.

Good luck.