Table:
text: List of tallest buildings in San Francisco
Tallest buildings
Tallest buildings
Rank_ Name_ Height_ft_m Floors Year_
38 Two Embarcadero Center 413 (126) 30 1974
40 595 Market Street 410 (125) 30 1979
41 123 Mission Street 407 (124) 29 1986
42 101 Montgomery 404 (123) 28 1984
42 Embarcadero West 404 (123) 34 1989
44 100 Van Ness Avenue 400 (122) 29 1974

text: List of tallest buildings in San Francisco
Tallest buildings
Tallest buildings
Rank_ Name_ Height_ft_m Floors Year_
25 45 Fremont Street 476 (145) 34 1978
27 333 Market Street 472 (144) 33 1979
28 650 California Street 466 (142) 34 1964
29 100 First Plaza 447 (136) 27 1988
30 One California 438 (134) 32 1969
31 San Francisco Marriott Marquis 436 (133) 39 1989
32 Russ Building 435 (132) 32 1927
32 140 New Montgomery 435 (132) 26 1925
34 The Infinity II 420 (128) 41 2009
34 JP MorganChase Building 420 (128) 31 2002
34 The Paramount 420 (128) 40 2002
37 Providian Financial Building 417 (127) 30 1981
38 Three Embarcadero Center 413 (126) 31 1977

Question: In the list of tallest buildings in San Francisco, what is the average number of stories of the building taller than 30 a year prior to 1977 and an address of 100 Van Ness Avenue?