$3.$ A hollow plastic sphere is held below the surface of a freshwater lake by a cord anchored

to the bottom of the lake. The sphere has a volume of $0\mathrm{.}650$ m$3$ and tension in the cord is $1420$

N$.$

a$)$ Calculate the buoyant force exerted by the water on the sphere.

b$)$ What is the mass of the sphere?

c$)$ The cord breaks and the sphere rise to the surface. When the sphere comes to rest,

what fraction of its volume is submerged?