The product$-$of$-$sum approach for the logic signal A when input signals are F$,$D$,$G$,$ and $R$ is:

$A=$prodM$(0,1,2,4,5,10,11,13,14,15)$

$A=(F+D+G+R)*(F+D+G\frac{+}{b}ar(R))*(F+D\frac{+}{b}ar(G)+R)*(F\frac{+}{b}ar(D)+G+R)*(F\frac{+}{b}ar(D)+G\frac{+}{b}ar(R))*(\frac{?}{\text{b}\text{a}\text{r}}(F)+D\frac{+}{b}ar(G)+R)*(\frac{?}{\text{b}\text{a}\text{r}}(F)+D\frac{+}{b}ar(G)\frac{+}{b}ar(R))*(\frac{?}{\text{b}\text{a}\text{r}}(F)\frac{+}{b}ar(D)+G\frac{+}{b}ar(R))*(\frac{?}{\text{b}\text{a}\text{r}}(F)\frac{+}{b}ar(D)\frac{+}{b}ar(G)+R)*(\frac{?}{\text{b}\text{a}\text{r}}(F)\frac{+}{b}ar(D)\frac{+}{b}ar(G)\frac{+}{b}ar(R))$

$A=(\frac{?}{\text{b}\text{a}\text{r}}(F)\frac{+}{b}ar(D)+G+R)*(\frac{?}{\text{b}\text{a}\text{r}}(F)+D+G\frac{+}{b}ar(R))*(\frac{?}{\text{b}\text{a}\text{r}}(F)+D+G+R)*(F\frac{+}{b}ar(D)\frac{+}{b}ar(G)\frac{+}{b}ar(R))*(F+D\frac{+}{b}ar(G)\frac{+}{b}ar(R))$

$A=F*D\frac{*}{b}ar(G)\frac{*}{b}ar(R)+F\frac{*}{b}ar(D)\frac{*}{b}ar(G)*R+F\frac{*}{b}ar(D)\frac{*}{b}ar(G)\frac{*}{b}ar(R)\frac{+}{b}ar(F)*D*G*R\frac{+}{b}ar(F)\frac{*}{b}ar(D)*G*R$

$A={\displaystyle \underset{?}{\overset{?}{}}}m(0,1,2,4,5,10,11,13,14,15)$