Answer:
Capacitance is 0.572×10⁻¹⁰ Farad
Explanation:
Radius = R₁ = 6.25 cm = 6.25×10⁻² m
Radius = R₂ = 15 cm = 15×10⁻² m
Dielectric constant = k = 4.8
Electric constant = ε₀ = 8.854×10⁻¹² F/m
ε/ε₀=k
ε=kε₀

∴ Capacitance is 0.572×10⁻¹⁰ Farad
Velocity is a vector quantity. A vector quantity has both a magnitude and a direction. Speed only has a magnitude, but no direction. Velocity has both.
I think that mechanism is called a <em>"lens turret"</em>.
To solve this problem we must consider the expressions of Stefan Boltzmann's law for which the rate of change of the radiation of energy H from a surface must be

Where
A = Surface area
e = Emissivity that characterizes the emitting properties of the surface
= Universal constant called the Stefan-Boltzmann constant 
T = Absolute temperature
The total heat loss would be then





Therefore the net rate of heat loss from the body by radiation is 155.29J