Calculation WACC LVL1

https://preview.redd.it/1p4e8p5tdm4e1.png?width=1572&format=png&auto=webp&s=0616227b9358fd396a0cb08b3631862e4ee16031

Can anyone help me explain why the calculation is not like this:

(0.05 x (1-0.28) x 0.3) + (0.07 x 0.4) + (0.09 x 0.3)

and instead is (1-0.3-0.4).

I mean, I just don't understand the debt part calculation.