How Are Christo and Jeanne-Claude's Site-Specific Works of Art Funded

How are Christo and Jeanne-Claude's site-specific works of art funded?

A) They are funded through grants from the National Endowment of the Arts and other funding agencies
B) They are commissioned by museums, individuals, and local governments.
C) They sell models, drawings, and other preliminary materials from the preceding project.
D) Admission fees for those who want to see the final work.