Ortega Company incurred the following costs for the months of January and February:

Assume that output was $1,000$ units in January and $3,000$ units in February, utility cost is a mixed cost, and the fixed cost of utilities was $$2,000.$ What is the variable rate per unit of output for utilities cost?

a$.$ $$0\mathrm{.}20$

b$.$ $$0\mathrm{.}30$

c$.$ $$0\mathrm{.}80$

d$.$ $$0\mathrm{.}60$