A homeowner wishes to build an enclosed porch adjoining west end of his home. The present distance between the owners home and west property line is 15 feet. If the owner builds the porch, the distance to the property line will be reduced to 5 feet. However, local requirements specify at least a 10 foot setback to legally construct his porch, the owner needs

a. to obtain a special-use permit.

b. to obtain a zoning variance.

c. to apply for a non-conforming-use status.

d. no special authorization.