Which of the Following Addition Problems Cannot Be Solved Accurately

Which of the following addition problems cannot be solved accurately when using a floating-point system in which each value is encoded by a byte whose most significant bit is the sign bit,the next three bits represent the exponent field in excess notation,and the last four bits represent the mantissa?

A) 2 1/2 + 1 3/8
B) 3 1/2 + 4 1/2
C) 7 + 3/4
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