C=2PIR
C=2*3.14*15
C=6.28*15
C=94.2 INCHES PER ROTATION.
94.2*800=75,360 IN/MIN.
75,360/12=6,280 FT/MIN.
6,280*60=376,800 FT/HR.
376,800/5280=71.36 MPH ANS.