A small ring is released from rest halfway up from the bottom of a half$-$pipe of radius $4$ m$.$ The ring

rolls without slipping. At the low point:

$21.$ The speed of the ring$$s center is:

a$)4\mathrm{.}47$ m$/$s

b$)4\mathrm{.}87$ m$/$s

c$)5\mathrm{.}27$ m$/$s

d$)5\mathrm{.}67$ m$/$s

e$)6\mathrm{.}07$ m$/$