BUYPLSE, Plz help me this is my very first experience in DSA Learning series

sample output is correct 28, then why not able to solve it correctly. Plz help me this is my very first experience in DSA Learning series.

def sum_total(a, b, x, y):
return (ax+by)

print(sum_total(2, 4, 4, 5))

(ax)+(by)
Multiply In Python With Examples - Python Guides.