A Disk Is Suspended by a Nail Such That the Pivots

Multiple Choice

A disk is suspended by a nail such that the pivots in a vertical plane about a point on the edge of the disk.If the period of oscillation of the disk is 1.25 s ,what is the disk's radius?

A) 26 cm
B) 78 cm
C) Cannot answer without knowing the disk's mass
D) 51 cm