If S₁,S₂, and Sₐ respectively denote the total surface area of a sphere, cylinder, and cone of radius r and height 2r, the relation between S₁, S₂, and Sₐ is equal to:
a) Sₐ=S₁+S₂
b) Sₐ=S₁-S₂
c) Sₐ=S₁xS₂
d) Sₐ=S₁/S₂