C, D is on ⊙O, AB is the diameter, DE is the tangent of ⊙O, DE⊥AE.
∴AC⊥BC AD⊥BD DE⊥OD
∴AE‖OD BC
△ ADB △ AGD △ AGD = △ AED △ AEF △ DOF
AF:DF=AE:OD AG=AE
AC:OG=AB:OD=2: 1
∫AC:AB = 3:5
∴OG:AO=3:5
AG:AO=8:5
AO=OD
Silver: outside diameter =8:5
AF:DF=8:5