Memo letterhead reading 'International Sasquatch Conservationg Society. Warren Atterbom, President. William Murray, Vice President.' The memo is encoded as follows: Rfc ylmlwkmsq rgn uc ucpc egtcl yzmsr rfc tcpw pcaclr qyqosyraf qgefrgleq gl rfc Qyl Zcplypbglm kmslryglq gq amppcar. Uc fytc y kyl iccngle yl cwc ml rfcgp ufcpcyzmsrq ylb ugjj qclb y rcyk msr fcpc rm aynrspc rfck dmp wms. Yuygrgle dsprfcp glqrpsargmlq. Ksaf rm bm. -Jcmlypb. Letters through the memo reveal the encoded phrase 'qytcqyqosyraf.mpe/tgeclcpc.frkj'
The International Sasquatch Society registration form. Name: Warren Atterbom. Born: XX/XX/1975. Sex: Blank. Blood type: Human. Occupation: Student. City: Berkeley. State: California. How did you find us?: Saw a flyer on campus and felt compelled to join. I've had a lifelong obsession with bigfoot and I want to help. Membership fee: $10 Student Fee. Copyright 1999 ISCS.6

How old was Warren when he joined?