n = 4 , so, divide the interval to 4 sections
and find the value of f(x) at the midpoint of each interval
So, from 2 to 6
x = 2 , 3 , 4 , 5 , 6
At x = 2.5
w = 1 , h = 3/2.5 + 1 = 2.2
wh = 2.2
at x = 3.5
w = 1 , h = 3/3.5 + 1 = 13/7
wh = 13/7
at x = 4.5
w = 1 , h = 3/4.5 + 1 = 5/3
wh = 5/3
at x = 5.5
w = 1 , h = 3/5.5 + 1 = 17/11
wh = 17/11
so, the sum of Riemann = 2.2 + 13/7 + 5/3 + 17/11 = 7.27