Solve the Problem $\frac { 3 } { 4 }$ Of the Supplies Will Get Through, but 9 Army Soldiers

Solve the problem.
-A certain army is engaged in guerrilla warfare. It has two ways of getting supplies to its troops: it can send a convoy up the river road or it can send a convoy overland through the jungle. On a given day, the guerrillas can watch only one of the two roads. If the convoy goes along the river and the guerrillas are there, the convoy will have to turn back and 6 army soldiers will be lost. If the convoy goes overland and encounters the guerrillas, $\frac { 3 } { 4 }$ of the supplies will get through, but 9 army soldiers will be lost. Each day a supply convoy travels one of the roads, and if the guerrillas are watching the other road, the convoy gets through with no losses. What is the optimal strategy for the guerrillas if they want to inflict maximum losses on the army?

A) 0 river, 1 land

B) $\frac { 2 } { 5 }$ river, $\frac { 3 } { 5 }$ land

C) $\frac { 3 } { 5 }$ river, $\frac { 2 } { 5 }$ land

D) $\frac { 1 } { 2 }$ river, $\frac { 1 } { 2 }$ land