Which function(s) correctly calculate(s) the largest possible number of employees in a binary tree hierarchical data structure representing a company's organizational chart?
a) def max_employees(levels) :
if levels == 0:
return 1
elif levels == 1:
return 2
else:
return 2 max_employees(levels - 1) + 1
b) def max_employees(levels) :
if levels == 0:
return 0
else:
return 2levels - 1
c) def max_employees(levels) :
if levels == 0:
return 1
else:
return 2 max_employees(levels - 1)
d) def max_employees(levels) :
count = 0
for i in range(levels) :
count += 2i
return count