What value is assigned to the variable named payment when the following code is executed?

decimal? paymentAmount $=$ null;

decimal payment $=$ paymentAmount $??9\mathrm{.}99$m;

Question $43$ options:

a$)$

$9\mathrm{.}99$

b$)$

null

c$)$

$10$

d$)$

$0$