Please show me how to solve this in clear steps and explainations.

Use deMorgan's theorem to find the complement of the following function of $3$ variables:

$f(x_1,x_2,x_3)=x_1(x_2+(x_3{)}^{\text{'}})+x_2(x_3{)}^{\text{'}}$

Select one:

a$.f^{\text{'}}(x_1,x_2,x_3)=((x_1{)}^{\text{'}}+(x_2{)}^{\text{'}}{x}_3)((x_2{)}^{\text{'}}+x_3)$

b$.f^{\text{'}}(x_1,x_2,x_3)=(x_1{)}^{\text{'}}((x_2{)}^{\text{'}}+x_3)+(x_2{)}^{\text{'}}{x}_3$

c$.f^{\text{'}}(x_1,x_2,x_3)=(x_1+x_2(x_3{)}^{\text{'}})(x_2+(x_3{)}^{\text{'}})$

d$.f^{\text{'}}(x_1,x_2,x_3)=(x_1{)}^{\text{'}}+(x_2{)}^{\text{'}}{x}_3+((x_2{)}^{\text{'}}+x_3)$