Answer should be -128.
Overall size of Instruction is : 24 bit.
There are 32 register , so to represent 32 register we need 5 Bit.
There are 49 instruction , so we need 6 bit to represent all instructions.
so, immediated operand: 24-6+2*5 = 8
so minimum number thatw e can represent with 8 bits is -(2^n-1) = -128