Can someone please help fix this program? I'm pretty new in Python. Every time I run this program it says :

Traceback (most recent call last):

File "E:/Python/delin.py", line 38, in <module>

discounted_total = regular_total - full_discount

TypeError: unsupported operand type(s) for -: 'float' and 'NoneType'

def find_discount(total):

if total <120:

discount = 0

else:

if total <300:

discount = 0.03*total

else:

if total <500:

discount = 0.05*total

else:

discount = 0.07*total

return discount

#---------------------------------------------------------------------------

#main program

beef = 8.49

pork = 6.12

chicken = 5.21

quantity_beef= input("How many pounds of beef were bought?")

quantity_pork = input("How many pounds of pork were bought")

quantity_chicken = input("How many pounds of chicken were bought?")

total_beef = beef * quantity_beef

total_pork = pork * quantity_pork

total_chicken = chicken * quantity_chicken

regular_total = total_beef + total_pork + total_chicken

full_discount = find_discount(regular_total)

discounted_total = regular_total - full_discount

print "The total is " + discounted_total

This is Python 2.7 btw.

Edit: also, the function on the top [find_discount(total)] has the normal indentations needed. But when posting this, the lines didn't indent