HIGH LOW METHOD WITH STEPPED FIXED COST

Please Sir ( highwai08) help me with this question:

The following data related to the overhead expenditure of contract cleaners ( for industrial cleaning ) at tow activity levels:
Square metres cleaned…12,750…15,100
Overhead……………………$75,950..$83,585
When more than 14,000 square metres are industrially cleaned, there will be a step up in fixed costs of $4,700.
Required:
How can I calculate the estimated total cost if 14,500 square metres are to be industrially cleaned?
Please I need your help sir. Thank you.