Getting error object not callable in my program

OS : Windows 7
Python 2.7

total=0
temp =0
i=0;
j=1;
counter=0
MIN_val = 100
MAX_val = 0
file = open("C:/Users/Shrikanth/Desktop/Report.csv")
csv_reader = csv.reader(file)
next(csv_reader)

for all in csv_reader:
FileName, Channel, OrgSize, TransSize = all
if Channel == "TimesNow_LB":
total_redn= (float(OrgSize)- float(TransSize))/float(OrgSize) * 100
counter = counter + 1
MIN_val(float(total_redn))
MAX_val(float(total_redn))
AVG_val(float(total_redn))

print counter
def MIN_val(num):
global MIN_val
if MIN_val > num:
MIN_val = num
print MIN_val
def MAX_val(num):
global MAX_val
if MAX_val < num:
MAX_val=num
print MAX_val

So i'm getting ''MIN_val(float(total_redn))
TypeError: 'int' object is not callable'' error.
Why does it happen and what is the solution?

No repository file or test is identified. Reproduce the supplied snippet under Python 2.7, then inspect the MIN_val and MAX_val assignments, function definitions, and calls; done means the example runs without the reported TypeError and the intended minimum and maximum values are produced.