Groups and Inverse order

["ADH"]

Hi all,

I'm trying to solve the following problem on groups.
a,) Let G be a group.  If a belongs to G, then the order of a is the
same as the order of its inverse.
b.) Let G be a group.  Let a,b belong to G.  Show that a and b have the
same order if b=g^(-1)ag, for some element g belonging to G.
c.) Let G be a group. Show that ab and ba have the same order.

I believe the right and left cancellation laws will come into play in
b.) and c.).