How this produce 30 output

Question

def add(x, y):
print("abc")
return x + y

def do_twice(func, x, y):
return func(func(x, y), func(x, y))

a = 5
b = 10

print(do_twice(add, a, b))

Answer 1

first it produce two 15 and then add them

Answer 2

return func(func(x,y),func(x,y))

first it adds x and y twice so now arguments are add(15,15) i.e you are saying

add(add(5,10),add(5,10))

that becomes add(15,15)

Answer 3

why this code adding 15,15 argument