The subject is a one acre commercial zoned site permitting office and retail uses. The subject is in an area of transition and the zoning code was re-written in 2010. The site is currently improved with a former single family residence constructed in 1910 that was converted to 4-family use in the 1970's. This would best be called a(an)?

An illegally permitted use

An illegally permitted but non-conforming use

An illegally permitted and non-conforming use

A legally permitted but non-conforming use