During the winter the coefficient of correlation for monthly snowfall in the north versus south sides of the city is 0.8. The other parameters for monthly snowfall (cm) is:

north side : mean (80) s.d. (25)

south side mean (90) s.d. (30)

The city's snow removal costs are $120 per cm. for the north side and $100 per cm for the south side and $5000 per month regardless of snowfall.

What is the standard deviation of the total cost of snow removal per month in the city^