Question

A person applying for a sales positions is offered an alernative salary plan.
Plan A:A bas salary of $600 per month plus a commission of 4% of the gross value for the month.
Plan B: A base salary of $700 per month plus a commission of 6% of the gross sales of the month in excess of $10,000

a) for each plan formulate a function (an equation) that expresses monthly earnings as a function of gross sales (x)
b) for what gross sales values is plan b preferable?

i need help!!!!

I will do the second:

EarningsB=700 + .06*(Sales-10000)

Write the equation for earnings under A. Then set them equal and solve for Sales.