A company has four projects that have to be assigned to three project managers. The respective success factor based on each project manager's experience is shown in the table below $($Note: Higher the number, the more successful that respective project manager is expected to be in that project.$)$ All four project must have a project manager attached to them. If LP is used to help in this assignment, and the selected decision variables are Xij, which represents that project manager i is assigned to project j$,$ what is the correct standard model of this situation? Select one: a$.$ Max $356$X$1+244$X$2+358$X$3$ s$.$t$.$ X$1$A$+$X$1$B$+$X$1$C$+$X$1$D$=1$ X$2$A$+$X$2$B$+$X$2$C$+$X$2$D$=1$ X$3$A$+$X$3$B$+$X$3$C$+$X$3$D$=1$ X$1$A$+$X$2$A$+$X$3$A$=1$ X$1$B$+$X$2$B$+$X$3$B$=1$ X$1$C$+$X$2$C$+$X$3$C$=1$ X$1$D$+$X$2$D$+$X$3$D$=1$ b$.$ Max $90$X$1$A$+90$X$1$B$+87$X$1$C$+89$X$1$D$+81$X$2$A$+85$X$2$B$+73$X$2$C$+86$X$2$D$+90$X$3$A$+84$X$3$B$+94$X$3$C$+90$X$3$D s$.$t$.$ X$1$A$+$X$1$B$+$X$1$C$+$X$1$D$>=1$ X$2$A$+$X$2$B$+$X$2$C$+$X$2$D$>=1$ X$3$A$+$X$3$B$+$X$3$C$+$X$3$D$>=1$ X$1$A$+$X$2$A$+$X$3$A$>=1$ X$1$B$+$X$2$B$+$X$3$B$>=1$ X$1$C$+$X$2$C$+$X$3$C$>=1$ X$1$D$+$X$2$D$+$X$3$D$>=1$ c$.$ Max $90$X$1$A$+90$X$1$B$+87$X$1$C$+89$X$1$D$+81$X$2$A$+85$X$2$B$+73$X$2$C$+86$X$2$D$+90$X$3$A$+84$X$3$B$+94$X$3$C$+90$X$3$D s$.$t$.$ X$1$A$+$X$1$B$+$X$1$C$+$X$1$D$=1$ X$2$A$+$X$2$B$+$X$2$C$+$X$2$D$=1$ X$3$A$+$X$3$B$+$X$3$C$+$X$3$D$=1$ X$1$A$+$X$2$A$+$X$3$A$=1$ X$1$B$+$X$2$B$+$X$3$B$=1$ X$1$C$+$X$2$C$+$X$3$C$=1$ X$1$D$+$X$2$D$+$X$3$D$=1$ d$.$ Max $90$X$1$A$+90$X$1$B$+87$X$1$C$+89$X$1$D$+81$X$2$A$+85$X$2$B$+73$X$2$C$+86$X$2$D$+90$X$3$A$+84$X$3$B$+94$X$3$C$+90$X$3$D s$.$t$.$ X$1$A$+$X$1$B$+$X$1$C$+$X$1$D$>=1$ X$2$A$+$X$2$B$+$X$2$C$+$X$2$D$>=1$ X$3$A$+$X$3$B$+$X$3$C$+$X$3$D$>=1$ X$1$A$+$X$2$A$+$X$3$A$=1$ X$1$B$+$X$2$B$+$X$3$B$=1$ X$1$C$+$X$2$C$+$X$3$C$=1$ X$1$D$+$X$2$D$+$X$3$D$=1$