A mountain climber with a mass M ponders the idea of attaching a helium-filled balloon to himself to reduce his weight, so his effective weight will be P*Mg, where P is a numerical factor in the range of 0.0 .. 1.0: When P = 0.0, the climber will be just barely floating above the surface When P = 1.0, there is no lifting at all Density of the Air = 1.21 kg/m3 Density of Helium = 0.178 kg/m3 If the balloon is perfectly spherical, calculate it's diameter provided the following values: M = 77 kg P = 0.2 .