Revision note, pg 32& 33, the MM theory

Hi Sir, i refer to you Revision note, pg 32& 33 regrading the MM theory and the example.

Company raised more debt and the gearing ratio change to 80% (debt to quity)

i am a bit confused with the gearing ratio.
since it meantioned gearing ratio change to 80% (debt to quity).

the market value of equity should be 100
the market value of debt should be 80
so total market value is 180

but how come the answer of new WACC, the total market value is 80+20, not 100+80 ?

AND,

in MM formula, the Cost of debt is always refer to risk free debt?