$($a$)$ Critically explain the Modigliani and Miller's $($MM$)$ proposition that capital structure does not affect the value of a firm, highlighting the assumptions required for this proposition to hold true.

$(40$ marks$)$

$($c$)$ Show clearly the impact of personal taxes on the firm value in a Modigliani and Miller universe. When would a firm be indifferent between issuing debt or equity?

$(20$ marks$)$