Suppose in a model we have data cells $($constant numbers$)$ N$1,$ N$2,$ N$3,$ and N$4$ and decision variable cells D$1,$ D$2,$ D$3,$ and D$4.$ Fill in the blank with L or N whether the following formulas are Linear or Non$-$linear. SUMPRODUCT$($D$1$:D$4,$ D$1$:D$4)$ D$1/$ D$2$ N$1^2*$ D$1+$ N$2*$ D$2$ IF$($D$1>=50,$ N$1,$ N$2)$ IF$($N$1>=50,$ D$1,$ D$2)$ D$1/($N$1+$ N$2+$ N$3)$ D$1*$ D$4+$ D$2*$ D$3$