What is the minimum cost of crashing the following project at Sawaya Robotics by $4$ days?

$\backslash$table$[[$ACTIVITY$,\backslash$table$[[$NORMAL$],[$TIME $($DAYS$)]],\backslash$table$[[$CRASH$],[$TIME $($DAYS$)]],\backslash$table$[[$NORMAL$],[$COST$]],\backslash$table$[[$CRASH$],[$COST$]],$IMMEDIATE PREDECESSOR$($S$)],[$Design $($A$),8,6,400,450,-],[$Wiring $($B$),6,5,1,000,1,100,-],[$Chip install $($C$),4,3,600,700,-],[$Software $($D$),5,3,1,000,1,300,$A$,$ B$],[$Testing $($E$),8,5,1,100,1,625,$C$]]$

The minimum cost of crashing the following project at Sawaya Robotics by $4$ days is $$900($enter your response as a whole number$).$