Write the sum in sigma notation.
1/2 + 2/3 + 3/4 + 4/5 + ... + 19/20
a) ¹⁸Σᵢ=₁ i/i+1
b) ¹⁹Σᵢ=₁ i/i+1
c) ¹⁹Σᵢ=₁ i/i+2
d) ²⁰Σᵢ=₁ i/i+1
e) ¹⁹Σᵢ=₁ i+1/i