Answer : 11,776
Expand Opcode Technique Question.
Two Address Instruction Formulation : 16 - 10 = 6 bits for Opcode. Total Possible Two Address Instructions = $2^6 = 64$
But System has only 40 Two Address Instructions, Thus, Unused combinations for first Six bits = 24
One Address Instruction Formulation : Total possible One Address Instructions = $24$ (Combinations for first 6 Bits) * $2^5$ = 768
But System has only 400 One Address Instructions, Thus, Unused combinations for first Ten bits = 368
Zero Address Instruction Formulation :
Total Possible One Address Instructions = 368 * $2^5$ = 11,776