I'm assigned to write a simple function which gives me the area under x^4 between an interval, but using a series of rectangles instead of a straight integral. I have to write a function that defines the minimum height of these rectangles and another function defining the maximum height, and then find the average value. I am a **total** newbie, so as trivial as it sounds, I've no clue how to define those functions.
I dont know how to make one define minimum heights and the other define maximum, and I don't think what I came up with as a sum of rectangles is correct.

def Smin(n):
sum=0
a=0
b=6
width=(b-a)/n
for i in range (1,n+1):
sum=width*(sum+i**4)
return sum

Any help will be greatly apreciated.