Arthur's Plumbing reported the following:

Revenues

Variable manufacturing costs

Variable nonmanufacturing costs

Fixed manufacturing costs

Fixed nonmanufacturing costs

$$4,500$

$ $900$

$ $810$

$ $630$

$ $545$

Required:

a$.$ Compute contribution margin.

b$.$ Compute contribution margin percentage.

c$.$ Compute gross margin.

d$.$ Compute gross margin percentage.

e$.$ Compute operating income.