Determine the missing amounts in each of these four separate situations a through $d.$

$\backslash$table$[[$Supplies available $-$ prior year$-$end,a$,$b$,$c$,$d$],[$$$,400,$$$,1,200,$$$,1,260],[$Supplies purchased during current year,,$2,800,,6,500,,-,3,000],[$Total supplies available,,$3,200,,7,700,,,],[$Supplies available $-$ current year$-$end,,$(650),,,,(1,350),(700)$