Express the sum using sigma notation: 1+5/6+6/8+7/10+8/12
a. the summation from k equals 2 to 6 of the quotient of k plus 1 and 2 times k
b. the summation from k equals 2 to 6 of the quotient of k plus 2 and 2 times k
c. the summation from k equals 2 to 6 of the quotient of k plus 2 and 2 raised to the k power
d. the summation from k equals 4 to 7 of the quantity 1 plus the quotient of k plus 1 and k plus 2